Esters containing aromatic groups as solvents for organic electronic formulations

ABSTRACT

The present invention relates to formulations for the preparation of organic electronic devices (OLEDs) which comprise (A) at least one specific ester solvent containing an aromatic group and (B) at least one organic functional material selected from organic conductors, organic semiconductors, organic fluorescent compounds, organic phosphorescent compounds, organic light-absorbent compounds, organic light-sensitive compounds, organic photosensitisation agents and other organic photoactive compounds, selected from organometallic complexes of transition metals, rare earth metals, lanthanides and actinides.

TECHNICAL FIELD

The present invention relates to formulations for the preparation oforganic electronic (OE) devices which comprise at least one estersolvent containing an aromatic group and at least one specific organicfunctional material. The formulation is particularly suitable for thepreparation of Organic Light Emitting Devices (OLEDs) by inkjet printingor spin coating processes.

BACKGROUND ART

OLEDs have been fabricated for a long time by vacuum depositionprocesses. Other techniques such as inkjet printing have been recentlythoroughly investigated because of their advantages such as cost savingsand scale-up possibilities. One of the main challenges in multilayerprinting is to identify and adjust the relevant parameters to obtain ahomogeneous deposition of inks on the substrate coupled with good deviceperformances. In particular, solubility of materials, physicalparameters of the solvent (surface tension, viscosity, boiling point,etc.), printing technology, processing conditions (air, nitrogen,temperature, etc.) and drying parameters are characteristics which candrastically influence the pixel pattern and thus the deviceperformances. Among these features, the choice of a suitable solvent iscrucial.

As an example, US 2014/0097406 A1 describes liquid compositions (e.g.inkjet fluids) for forming an organic layer of an organic electronicdevice (e.g. OLED). The liquid composition comprises a small moleculeorganic semiconductor material mixed in a solvent in which the solventis represented by:

wherein R^(a) is C₁₋₆ alkyl; R^(b) is C₁₋₆ alkyl; and R^(c) is one ormore optional substituents independently selected from C₁₋₆ alkyl andaryl. As an example, methyl phenoxyacetate (MPA) is used as solvent inthe liquid composition according to US 2014/0097406 A1.

In a similar way, US 2011/0220886 A1 describes organicelectroluminescence material compositions which include a solvent havingan aliphatic ring or an aromatic ring and an anthracene derivative.Dimethyl phthalate, 2-ethylphenyl acetate and o-tolyl acetate arementioned as specific examples of the solvent in US 2011/0220886 A1.

From WO 2010/010337 A1 compositions for manufacturing light-emissivedevices are known which are based on a solvent system comprising butylbenzoate (40% by volume), methyl benzoate (40% by volume) and 4-methylanisole (20% by volume).

Technical Problem and Object of the Invention

Many solvents have been proposed in organic electronic devices forinkjet printing as described above. However, the number of importantparameters playing a decisive role during deposition and the dryingprocess makes the choice of the solvent very challenging. Thus, theformulations containing organic functional materials such assemiconductors used for deposition by inkjet printing still need to beimproved. It has been found by the present inventors that certainorganic light-emissive materials are particularly difficult to depositeffectively using inkjet printing type techniques. In particular, thepresent inventors have found that compositions comprising asemi-conductive organic host material and a luminescent metal complexcan give poor printing performance using standard solvents. For example,the use of standard solvents for such compositions has been found togive very poor drop directionality. Accordingly, the present applicanthas sought to develop solvent systems specifically adapted for printingsuch compositions.

One object of the present invention is to provide a formulation of anorganic functional material which allows a controlled deposition to formorganic semiconductor layers having good layer properties andperformance. A further object of the present invention is to provide aformulation of an organic functional material which allows an uniformapplication of ink droplets on a substrate when used in an inkjetprinting method thereby giving good layer properties and performance.

Solution to Problem

The above-mentioned objects of the present invention are solved byproviding a formulation comprising

-   -   (A) at least one ester solvent according to General Formula (I)        or General Formula (II):

-   -   wherein R¹ is H or R³; R² is H or R³; and R³ may be the same or        different from each other and is on each occasion selected        independently from the group consisting of hydrogen,        straight-chain alkyl groups having from 1 to 12 carbon atoms,        straight-chain alkenyl or alkynyl groups having from 2 to 12        carbon atoms, branched-chain alkyl or alkenyl groups having from        3 to 12 carbon atoms and branched-chain alkynyl groups having        from 4 to 12 carbon atoms, wherein one or more non-adjacent CH₂        groups may be optionally replaced by —O—, —S—, or —Si(R⁵)₂—; or    -   R¹ and R² taken together represent ═CH₂; and R³ is selected from        the group consisting of hydrogen, straight-chain alkyl groups        having from 1 to 12 carbon atoms, straight-chain alkenyl or        alkynyl groups having from 2 to 12 carbon atoms, branched-chain        alkyl or alkenyl groups having from 3 to 12 carbon atoms and        branched-chain alkynyl groups having from 4 to 12 carbon atoms,        wherein one or more non-adjacent CH₂ groups may be optionally        replaced by —O—, —S—, or —Si(R⁵)₂—; and    -   wherein X on each occasion is selected independently from N or        CR⁴ with the provision that no more than three X are selected as        N;    -   R⁴ on each occasion is selected independently from the group        consisting of hydrogen, straight-chain alkyl or alkoxy groups        having from 1 to 12 carbon atoms, straight-chain alkenyl or        alkynyl groups having from 2 to 12 carbon atoms, branched-chain        alkyl, alkoxy or alkenyl groups having from 3 to 12 carbon        atoms, branched-chain alkynyl groups having from 4 to 12 carbon        atoms and SiR⁵ ₃;    -   R⁵ on each occasion is selected independently from the group        consisting of hydrogen, straight-chain alkyl or alkoxy groups        having from 1 to 12 carbon atoms and branched-chain alkyl or        alkoxy groups having from 3 to 12 carbon atoms;    -   Q¹ is absent or an alkylene group having from 1 to 10 carbon        atoms which may optionally contain one or more double bonds and        which may optionally be substituted with one or more alkyl        groups having from 1 to 4 carbon atoms, wherein two alkyl groups        may be bonded together to form a monocyclic ring system together        with the carbon atoms of said alkylene group; and    -   Q² is absent or an alkylene group having from 1 to 10 carbon        atoms which may optionally contain one or more double bonds and        which may optionally be substituted with one or more alkyl        groups having from 1 to 4 carbon atoms, wherein two alkyl groups        may be bonded together to form a monocyclic ring system together        with the carbon atoms of said alkylene group;    -   with the proviso that if Q¹ is absent, R³ is not hydrogen; and    -   with the proviso that if Q² is absent, X on each occasion is        CR⁴, wherein at least one R⁴ is a straight-chain alkoxy group        having from 1 to 12 carbon atoms or a branched-chain alkoxy        group having from 3 to 12 carbon atoms; and    -   (B) at least one organic functional material selected from the        group consisting of organic conductors, organic semiconductors,        organic fluorescent compounds, organic phosphorescent compounds,        organic light-absorbent compounds, organic light-sensitive        compounds, organic photosensitisation agents and other organic        photoactive compounds, selected from organometallic complexes of        transition metals, rare earth metals, lanthanides and actinides.

Advantageous Effects of Invention

The inventors have surprisingly found that the use of an estercontaining an aromatic group as solvent for OLED formulations allows aneffective ink deposition to form uniform and well-defined organic layersof functional materials which have very good layer properties and showvery good performance.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows a typical layer structure of a device containing asubstrate, an ITO anode, a hole-injection layer (HIL), a hole-transportlayer (HTL), a green-emissive layer (G-EML), a hole blocking layer(HBL), an electron-transport layer (ETL) and an Al cathode.

DESCRIPTION OF EMBODIMENTS

The present invention relates to a formulation comprising

-   -   (A) at least one ester solvent according to General Formula (I)        or General Formula (II):

-   -   wherein R¹ is H or R³; R² is H or R³; and R³ may be the same or        different from each other and is on each occasion selected        independently from the group consisting of hydrogen,        straight-chain alkyl groups having from 1 to 12 carbon atoms,        straight-chain alkenyl or alkynyl groups having from 2 to 12        carbon atoms, branched-chain alkyl or alkenyl groups having from        3 to 12 carbon atoms and branched-chain alkynyl groups having        from 4 to 12 carbon atoms, wherein one or more non-adjacent CH₂        groups may be optionally replaced by —O—, —S—, or —Si(R⁵)₂—; or        R¹ and R² taken together represent ═CH₂; and R³ is selected from        the group consisting of hydrogen, straight-chain alkyl groups        having from 1 to 12 carbon atoms, straight-chain alkenyl or        alkynyl groups having from 2 to 12 carbon atoms, branched-chain        alkyl or alkenyl groups having from 3 to 12 carbon atoms and        branched-chain alkynyl groups having from 4 to 12 carbon atoms,        wherein one or more non-adjacent CH₂ groups may be optionally        replaced by —O—, —S—, or —Si(R⁵)₂—; and    -   wherein X on each occasion is selected independently from N or        CR⁴ with the provision that no more than three X are selected as        N;    -   R⁴ on each occasion is selected independently from the group        consisting of hydrogen, straight-chain alkyl or alkoxy groups        having from 1 to 12 carbon atoms, straight-chain alkenyl or        alkynyl groups having from 2 to 12 carbon atoms, branched-chain        alkyl, alkoxy or alkenyl groups having from 3 to 12 carbon        atoms, branched-chain alkynyl groups having from 4 to 12 carbon        atoms and SiR⁵ ₃;    -   R⁵ on each occasion is selected independently from the group        consisting of hydrogen, straight-chain alkyl or alkoxy groups        having from 1 to 12 carbon atoms and branched-chain alkyl or        alkoxy groups having from 3 to 12 carbon atoms;    -   Q¹ is absent or an alkylene group having from 1 to 10 carbon        atoms which may optionally contain one or more double bonds and        which may optionally be substituted with one or more alkyl        groups having from 1 to 4 carbon atoms, wherein two alkyl groups        may be bonded together to form a monocyclic ring system together        with the carbon atoms of said alkylene group; and    -   Q² is absent or an alkylene group having from 1 to 10 carbon        atoms which may optionally contain one or more double bonds and        which may optionally be substituted with one or more alkyl        groups having from 1 to 4 carbon atoms, wherein two alkyl groups        may be bonded together to form a monocyclic ring system together        with the carbon atoms of said alkylene group;    -   with the proviso that if Q¹ is absent, R³ is not hydrogen; and    -   with the proviso that if Q² is absent, X on each occasion is        CR⁴, wherein at least one R⁴ is a straight-chain alkoxy group        having from 1 to 12 carbon atoms or a branched-chain alkoxy        group having from 3 to 12 carbon atoms; and    -   (B) at least one organic functional material selected from the        group consisting of organic conductors, organic semiconductors,        organic fluorescent compounds, organic phosphorescent compounds,        organic light-absorbent compounds, organic light-sensitive        compounds, organic photosensitisation agents and other organic        photoactive compounds, selected from organometallic complexes of        transition metals, rare earth metals, lanthanides and actinides.

PREFERRED EMBODIMENTS

In a 1^(st) preferred embodiment, the ester solvent according to GeneralFormula (I) is selected from the group consisting of General Formulae(I-a) to (I-i):

-   -   and the ester solvent according to General Formula (II) is        selected from the group consisting of General Formulae (II-a) to        (II-i):

-   -   wherein in General Formulae (I-a) to (I-i) and (II-a) to (II-i)        each X is CR⁴;    -   R⁴ on each occasion is selected independently from the group        consisting of hydrogen, straight-chain alkyl or alkoxy groups        having from 1 to 12, preferably from 1 to 6, carbon atoms,        straight-chain alkenyl or alkynyl groups having from 2 to 12,        preferably from 2 to 6, carbon atoms, branched-chain alkyl,        alkoxy or alkenyl groups having from 3 to 12, preferably from 3        to 6, carbon atoms, branched-chain alkynyl groups having from 4        to 12, preferably from 4 to 6, carbon atoms and SiR⁵ ₃;    -   R⁵ on each occasion is selected independently from the group        consisting of hydrogen, straight-chain alkyl or alkoxy groups        having from 1 to 12, preferably from 1 to 6, carbon atoms and        branched-chain alkyl or alkoxy groups having from 3 to 12,        preferably from 3 to 6, carbon atoms; and    -   R¹, R² and R³ are defined as in General Formula (I) above;    -   wherein in General Formulae (I-a) to (I-i) Q¹ is absent or an        alkylene group having from 1 to 6, preferably from 1 to 3,        carbon atoms which may optionally contain one or more double        bonds and which may optionally be substituted with one or more        alkyl groups having from 1 to 4 carbon atoms, wherein two alkyl        groups may be bonded together to form a monocyclic ring system        together with the carbon atoms of said alkylene group; and    -   wherein in General Formulae (II-a) to (II-i) Q² is an alkylene        group having from 1 to 6, preferably from 1 to 3, carbon atoms        which may optionally contain one or more double bonds and which        may optionally be substituted with one or more alkyl groups        having from 1 to 4 carbon atoms, wherein two alkyl groups may be        bonded together to form a monocyclic ring system together with        the carbon atoms of said alkylene group.

In a 2^(nd) preferred embodiment, the substituents R⁴ and R⁵ in GeneralFormula 1 and General Formula 2 are defined as follows:

-   -   R⁴ on each occasion is selected independently from the group        consisting of hydrogen, straight-chain alkyl or alkoxy groups        having from 1 to 6 carbon atoms, straight-chain alkenyl or        alkynyl groups having from 2 to 6 carbon atoms, branched-chain        alkyl, alkoxy or alkenyl groups having from 3 to 6 carbon atoms,        branched-chain alkynyl groups having from 4 to 6 carbon atoms        and SiR⁵ ₃;    -   R⁵ on each occasion is selected independently from the group        consisting of hydrogen, straight-chain alkyl or alkoxy groups        having from 1 to 6 carbon atoms and branched-chain alkyl or        alkoxy groups having from 3 to 6 carbon atoms.    -   The definition of R⁴ according to the 2^(nd) preferred        embodiment applies correspondingly to the proviso relating to        the absence of Q². This means that if Q² is absent in the 2^(nd)        preferred embodiment, X on each occasion is CR⁴, wherein at        least one R⁴ is a straight-chain alkoxy group having from 1 to 6        carbon atoms or a branched-chain alkoxy group having from 3 to 6        carbon atoms.

In a 3^(rd) preferred embodiment, the ester solvent according to GeneralFormula (I) is selected from the group consisting of General Formulae(I-a1), (I-a2), (I-a3), (I-c1) and (I-d1):

-   -   wherein each X is CR⁴; and    -   R¹, R², R³, R⁴ and Q¹ are defined as above.

In a 4^(th) preferred embodiment, the ester solvent according to GeneralFormula (II) is selected from the group consisting of General Formulae(II-a1), (II-a2), (II-a3), (II-c1) and (II-d1):

-   -   wherein each X is CR⁴; and    -   R¹, R², R³, R⁴ and Q² are defined as above.

It is preferred in any one of General Formulae (I) and (II), any one ofGeneral Formulae (I-a) to (I-i) and (II-a) to (II-i) and any one ofGeneral Formulae (I-a1), (I-a2), (I-a3), (I-c1), (I-d1), (II-a1),(II-a2), (II-a3), (II-c1) and (II-d1)

-   -   that R¹ is H or R³; R² is H or R³; and R³ on each occasion is        selected independently from the group consisting of hydrogen,        methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl,        nonyl and decyl and their isomers; or    -   that R¹ and R² taken together represent ═CH₂; and R³ is selected        from the group consisting of hydrogen, methyl, ethyl, propyl,        butyl, pentyl, hexyl, heptyl, octyl, nonyl and decyl and their        isomers.

It is even more preferred in any one of General Formulae (I) and (II),any one of General Formulae (I-a) to (I-i) and (II-a) to (II-i) and anyone of General Formulae (I-a1), (I-a2), (I-a3), (I-c1), (I-d1), (II-a1),(II-a2), (II-a3), (II-c1) and (II-d1)

-   -   that R¹ is H or R³; R² is H or R³; and R³ on each occasion is        selected independently from the group consisting of hydrogen,        methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl,        sec-butyl, t-butyl, n-pentyl, 2-pentyl, 3-pentyl, 2-methylbutyl,        3-methylbutyl, 3-methylbut-2-yl, 2-methylbut-2-yl,        2,2-dimethylpropyl, n-hexyl, 2-hexyl, 3-hexyl, 2-methylpentyl,        3-methylpentyl, 4-methylpentyl, 2-methylpent-2-yl,        3-methylpent-2-yl, 2-methylpent-3-yl, 3-methylpent-3-yl,        2-ethylbutyl, 3-ethylbutyl, 2,3-dimethylbutyl,        2,3-dimethylbut-2-yl, 2,2-dimethylbutyl, n-heptyl, n-octyl,        n-nonyl and n-decyl; or    -   that R¹ and R² taken together represent ═CH₂; and R³ is selected        from the group consisting of hydrogen, methyl, ethyl, n-propyl,        iso-propyl, n-butyl, iso-butyl, sec-butyl, t-butyl, n-pentyl,        2-pentyl, 3-pentyl, 2-methylbutyl, 3-methylbutyl,        3-methylbut-2-yl, 2-methylbut-2-yl, 2,2-dimethylpropyl, n-hexyl,        2-hexyl, 3-hexyl, 2-methylpentyl, 3-methylpentyl,        4-methylpentyl, 2-methylpent-2-yl, 3-methylpent-2-yl,        2-methylpent-3-yl, 3-methylpent-3-yl, 2-ethylbutyl,        3-ethylbutyl, 2,3-dimethylbutyl, 2,3-dimethylbut-2-yl,        2,2-dimethylbutyl, n-heptyl, n-octyl, n-nonyl and n-decyl.

It is preferred in General Formula (I) and in any one of thecorresponding subformulae (I-a) to (I-i), (I-a1), (I-a2), (la-3), (I-c1)and (I-d1) that

-   -   Q¹ is absent or an alkylene group having from 1 to 6 carbon        atoms, more preferably from 1 to 4 carbon atoms, which may        optionally contain one or more double bonds and which may        optionally be substituted with one or more alkyl groups having        from 1 to 4 carbon atoms, more preferably from 1 to 2 carbon        atoms, wherein two alkyl groups may be bonded together to form a        monocyclic ring system, more preferably a monocyclic five- or        six-membered ring system, together with the carbon atoms of said        alkylene group.

It is even more preferred in General Formula (I) and in any one of thecorresponding subformulae (I-a) to (I-i), (I-a1), (I-a2), (la-3), (I-c1)and (I-d1) that Q¹ is absent.

It is preferred in General Formula (II) and in any one of thecorresponding subformulae (II-a) to (II-i), (II-a1), (II-a2), (II-a3),(II-c1) and (II-d1) that

-   -   Q² is an alkylene group having from 1 to 6 carbon atoms, more        preferably from 1 to 4 carbon atoms, which may optionally        contain one or more double bonds and which may optionally be        substituted with one or more alkyl groups having from 1 to 4        carbon atoms, more preferably from 1 to 2 carbon atoms, wherein        two alkyl groups may be bonded together to form a monocyclic        ring system, more preferably a monocyclic five- or six-membered        ring system, together with the carbon atoms of said alkylene        group.

Preferred examples of the ester solvent represented by General Formula(I) are:

Particularly preferred examples of the ester solvent represented byGeneral Formula (I) are:

Preferred examples of the ester solvent represented by General Formula(II) are

The particularly preferred ester solvents according to General Formulae(I) and (II), their boiling points (BP) and physical state at roomtemperature (RT) are shown in Table 1 below.

TABLE 1 Preferred and most preferred ester solvents, their boilingpoints (BP) and their physical state at room temperature (RT). BP (° C.)Ester Sovlent Physical State

215° C. at 760 mm Hg Liquid at RT CAS: 637-27-4 Phenyl propionate

229° C. at 760 mm Hg Liquid at RT CAS: 4346-18-3 Butyric acid phenylester

231° C. at 760 mm Hg 110° C./ 10 mm Hg Liquid at RT CAS: 51233-77-3Propionic acid m-tolyl ester

224° C. at 760 mm Hg Liquid at RT CAS: 20279-29-2 Isobutyric acid phenylester

237° C. at 760 mm Hg Liquid at RT CAS: 103-93-5 Isobutyric acid p-tolylester

245° C. at 760 mm Hg 104° C. at 7 mm Hg Liquid at RT CAS: 36438-55-8Isobutyric acid m-tolyl ester

246° C. at 760 mm Hg Liquid at RT CAS: 51233-78-4 2,4-Xylyl propanoate

243° C. at 760 mm Hg Liquid at RT CAS: 51233-82-0 3,5-Xylyl propanoate

254° C. at 760 mm Hg Liquid at RT CAS: 859078-50-5 Propionic acid4-ethyl-2-methyl-phenyl ester

260° C. at 760 mm Hg Liquid at RT CAS: 448251-53-4 Propionic acid4-(methylethyl)-phenyl ester

248° C. at 760 mm Hg Liquid at RT CAS: 67001-64-3 Propionic acid3-methoxy-phenyl ester

263° C. at 760 mm Hg 158° C. at 38 mm Hg Liquid at RT CAS: 13098-94-7Propionic acid 4-methoxy-phenyl ester

240° C. at 760 mm Hg 102° C. at 12 mm Hg Liquid at RT CAS: 98491-60-23-Pyridyl propanoate

256° C. at 760 mm Hg Liquid at RT CAS: 96254-07-83-Pyridyl-2,2-dimethylpropanoate

236° C. at 760 mm Hg Liquid at RT CAS: 74669-30-0 4-Pyridyl propanoate

254° C. at 760 mm Hg 89-90° C. at 12 mm Hg Liquid at RT CAS: 2177-70-0Phenyl methacrylate

276° C. at 760 mm Hg Liquid at RT CAS: 1452165-31-94-Trimethylsilanyl-phenylpropanoate

206° C. at 760 mm Hg Liquid at RT CAS: 140-11-4 Benzyl acetate

250° C. at 760 mm Hg Liquid at RT CAS: 103-38-8 Benzyl isovalerate

240° C. at 760 mm Hg Liquid at RT CAS: 103-37-7 Benzyl butyrate

268° C. at 760 mm Hg Liquid at RT CAS: 140-26-1 Phenethyl isovalerate

263° C. at 760 mm Hg Liquid at RT CAS: 6290-37-5 Phenethyl hexanoate

271° C. at 760 mm Hg Liquid at RT CAS: 103-36-6 Ethyl cinnamate

220° C. at 760 mm Hg Liquid at RT CAS: 7335-26-4 Ethyl 2-methoxybenzoate

273° C. at 760 mm Hg Liquid at RT CAS: 10529-22-0 Ethyl3-methoxybenzoate

263° C. at 760 mm Hg Liquid at RT CAS: 94-30-4 Ethyl 4-methoxybenzoate

Preferably, the ester solvent according to General Formulae (I) and (II)and any one of the above-mentioned subformulae is liquid at roomtemperature which means that it has a melting point of 25° C. or below.

Preferably, the ester solvent according to General Formulae (I) and (II)and any one of the above-mentioned subformulae has a boiling point of400° C. or below, preferably in the range from 100° C. to 350° C., morepreferably in the range from 150° C. to 300° C. and most preferably inthe range from 200° C. to 290° C., wherein the boiling point is measuredat a pressure of 760 mm Hg.

Preferably, the formulation according to the present invention has aviscosity in the range from 0.8 to 50 mPa·s, preferably in the rangefrom 1 to 40 mPa·s, more preferably in the range from 2 to 20 mPa·s andmost preferably in the range from 2 to 10 mPa·s.

The viscosity of the formulations of the present invention can bemeasured by any standardized measurement method which allows ameasurement under standard conditions and calibration by a certifiedstandard. Due to the calibration, such standardized methods provideresults with high accuracy and low deviation, irrespective of themeasurement method used. As used herein, low deviation shall mean arelative error gap of about +/−10%, preferably +/−5%, between twodifferent standardized measurement methods. The skilled person is awarethat such an error gap is within the expected measurement accuracy andhas no significant impact on the outcome of the present invention.

Preferably, the viscosity of the formulations of the present inventionis measured with a 1° cone-plate rotational rheometer of the type HaakeMARS III Rheometer (Thermo Scientific). The equipment allows a precisecontrol of the temperature and sheer rate. The measurement of theviscosity is carried out at a temperature of 23.4° C. (+/−0.2° C.) and asheer rate of 500 s⁻¹. Each sample is measured three times and theobtained measured values are averaged. The measurement and processing ofdata is carried out using the software “Haake RheoWin Job Manager”according to DIN 1342-2. The Haake MARS III Rheometer is regularlycalibrated and the tool received a certified standard factorycalibration before first use.

Alternatively, the viscosity of the formulations of the presentinvention can be measured using a TA Instruments ARG2 Rheometer over ashear rate range of 10 to 1000 s⁻¹ using 40 mm parallel plate geometry.The measurement is taken as an average between 200 to 800 s⁻¹ where thetemperature and sheer rate are exactly controlled. The viscosities aremeasured at a temperature of 25° C. and a sheer rate of 500 s⁻¹. Eachsample is measured three times and the obtained viscosity value isaveraged over said measurements. The TA Instruments ARG2 Rheometer isregularly calibrated and the tool received a certified standard factorycalibration before first use.

Preferably, the organic solvent blend has a surface tension in the rangefrom 15 to 80 mN/m, more preferably in the range from 20 to 60 mN/m,most preferably in the range from 25 to 40 mN/m and especiallypreferably in the range from 28 to 35 mN/m.

The surface tension of the formulations of the present invention can bemeasured by any standardized measurement method which allows ameasurement under standard conditions and calibration by a certifiedstandard. Due to the calibration, such standardized methods providemeasurement results with high accuracy and low deviation, irrespectiveof the measurement method used. As used herein, low deviation shall meana relative error gap of about +/−10%, preferably +/−5%, between twodifferent standardized measurement methods. The skilled person is awarethat such an error gap is within the expected measurement accuracy andhas no significant impact on the outcome of the present invention.

Preferably, the surface tension of the formulations of the presentinvention is measured using the high precision drop shape analysis toolDSA100 from Krüss GmbH. The surface tension is determined by thesoftware “DSA4” in accordance with DIN 55660-1. All measurements areperformed at room temperature in the range between 22° C. and 24° C. Thestandard operating procedure includes the determination of the surfacetension of each formulation (sample volume of 0.3 mL) using a freshdisposable drop dispensing system (syringe and needle). Each drop ismeasured over the duration of one minute with sixty measurements whichare later on averaged. For each formulation three drops are measured.The final value is averaged over said measurements. The tool isregularly cross-checked against various liquids having known surfacetension.

Alternatively, the surface tension of the formulations of the presentinvention can be measured using a FTA (First Ten Angstrom) 1000 contactangle goniometer at 20° C. Details of the method are available fromFirst Ten Angstrom as published by Roger P. Woodward, Ph.D. “SurfaceTension Measurements Using the Drop Shape Method”. Preferably, thependant drop method can be used to determine the surface tension. Allmeasurements were performed at room temperature being in the rangebetween 20° C. and 22° C. For each formulation three drops are measured.The final value is averaged over said measurements. The tool isregularly cross-checked against various liquids having well knownsurface tensions.

Preferably, the content of the ester solvent according to GeneralFormulae (I) and (II) and any one of the above-mentioned subformulae isin the range from 0.5 to 100 vol.-%, more preferably from 1 to 95vol.-%, still more preferably from 10 to 90 vol.-% and most preferablyfrom 20 to 80 vol.-%, based on the total amount of solvents in theformulation. In a preferred embodiment, the content of the ester solventaccording to General Formulae (I) and (II) and any one of theabove-mentioned subformulae is 100 vol.-%, based on the total amount ofsolvents in the formulation.

The formulation may further comprise at least one additional solventwhich is different from the ester solvent. Suitable additional solventsare preferably solvents which include inter alia alcohols, aldehydes,ketones, ethers, esters, amides such as (C₁₋₂-alkyl)₂NH—CO—H, sulfurcompounds, nitro compounds, hydrocarbons, halogenated hydrocarbons (e.g.chlorinated hydrocarbons), aromatic or heteroaromatic hydrocarbons andhalogenated aromatic or heteroaromatic hydrocarbons.

Preferably, the additional solvent is selected from the group consistingof substituted and non-substituted aromatic or linear esters such asethyl benzoate, butyl benzoate; substituted and non-substituted aromaticor linear ethers such as 3-phenoxytoluene or anisole derivatives;substituted or non-substituted arene derivatives such as xylene; indanederivatives such as hexamethylindane; substituted and non-substitutedaromatic or linear ketones; substituted and non-substituted heterocyclessuch as pyrrolidinones, pyridines; fluorinated or chlorinatedhydrocarbons; and linear or cyclic siloxanes.

Particularly preferred additional solvents are, for example,1,2,3,4-tetramethylbenzene, 1,2,3,5-tetramethylbenzene,1,2,3-trimethylbenzene, 1,2,4,5-tetramethylbenzene,1,2,4-trichlorobenzene, 1,2,4-trimethylbenzene, 1,2-dihydronaphthalene,1,2-dimethylnaphthalene, 1,3-benzo-dioxolane, 1,3-diisopropylbenzene,1,3-dimethylnaphthalene, 1,4-benzo-dioxane, 1,4-diisopropylbenzene,1,4-dimethylnaphthalene, 1,5-dimethyl-tetralin, 1-benzothiophene,1-chloromethylnaphthalene, 1-ethylnaphthalene, 1-methoxynaphthalene,1-methylnaphthalene, 1-methylindole, 2,3-benzofuran,2,3-dihydrobenzofuran, 2,3-dimethylanisole, 2,4-dimethylanisole,2,5-dimethylanisole, 2,6-dimethylanisole, 2,6-dimethylnaphthalene,2-ethoxynaphthalene, 2-ethylnaphthalene, 2-isopropylanisole,2-methylanisole, 2-methylindole, 3,4-dimethylanisole,3,5-dimethylanisole, 3-methylanisole, 4-methylanisole, 5-decanolide,5-methoxyindane, 5-methoxyindole, 5-tert-butyl-m-xylene,6-methylquinoline, 8-methylquinoline, acetophenone, anisole,benzonitrile, benzothiazole, benzyl acetate, butyl benzoate, butylphenyl ether, cyclohexylbenzene, decahydronaphthol, dimethoxytoluene,3-phenoxytoluene, 4-phenoxytoluene; diphenyl ether, propiophenone,ethylbenzene, ethyl benzoate, γ-terpinene, hexylbenzene, indane,hexamethylindane, indene, isochroman, cumene, m-cymene, mesitylene,methyl benzoate, o-, m-, p-xylene, propylbenzoate, propylbenzene,o-dichlorobenzene, pentylbenzene, phenetol, ethoxybenzene, phenylacetate, p-cymene, propiophenone, sec-butylbenzene, t-butylbenzene,thiophene, toluene, veratrol, monochlorobenzene, o-dichlorobenzene,pyridine, pyrazine, pyrimidine, pyrrolidinone, morpholine,dimethylacetamide, dimethyl sulfoxide, decaline and/or mixtures of thesecompounds.

These solvents can be employed individually or as a mixture of two,three or more solvents forming the additional solvent.

Preferably, the organic functional material has a solubility in therange from 1 to 250 g/I in the respective solvent or solvent mixtureforming the basis of the formulation of the present invention.

The content of the organic functional material in the formulation ispreferably in the range from 0.001 to 20 weight-%, preferably in therange from 0.01 to 10 weight-%, more preferably in the range from 0.1 to5 weight-% and most preferably in the range from 0.5 to 3 weight-%,based on the total weight of the formulation.

The formulation of the present invention comprises at least one organicfunctional material which can be employed for the production offunctional layers of electronic devices. Organic functional materialsare generally the organic materials which are introduced between theanode and the cathode of an electronic device.

The organic functional material is selected from the group consisting oforganic conductors, organic semiconductors, organic fluorescentcompounds, organic phosphorescent compounds, organic light-absorbentcompounds, organic light-sensitive compounds, organic photosensitisationagents and other organic photoactive compounds, selected fromorganometallic complexes of transition metals, rare earth metals,lanthanides and actinides.

Preferably, the organic functional material is selected from the groupconsisting of fluorescent emitters, phosphorescent emitters, hostmaterials, matrix materials, exciton-blocking materials,electron-transport materials, electron-injection materials,hole-transport materials, hole-injection materials, n-dopants,p-dopants, wide-band-gap materials, electron-blocking materials andhole-blocking materials.

Preferred embodiments of organic functional materials are disclosed indetail in WO 2011/076314 A1, the content of which is incorporated intothe present application by way of reference.

More preferably, the organic functional material is an organicsemiconductor selected from the group consisting of hole-injectionmaterials, hole-transport materials, fluorescent emitters,phosphorescent emitters, electron-transport materials,electron-injection materials and buffer materials.

Most preferably, the organic semiconductor is selected from the groupconsisting of hole-transport materials, fluorescent emitters,phosphorescent emitters and buffer materials.

The organic functional material can be a compound having a low molecularweight, a polymer, an oligomer or a dendrimer, where the organicfunctional material may also be in the form of a mixture. In a preferredembodiment the formulations according to the invention may comprise twodifferent organic functional materials having a low molecular weight,one compound having a low molecular weight and one polymer or twopolymers (blend). In a further preferred embodiment the formulationsaccording to the invention may comprise up to five different organicfunctional materials which are selected from compounds having a lowmolecular weight or from polymers.

Preferably, the organic functional material is a compound having a lowmolecular weight. A low molecular weight is a weight of ≤3,000 g/mol,particularly preferably ≤2,000 g/mol and especially preferably ≤1,800g/mol. In case the organic functional material is a polymer, oligomer ordendrimer, the molecular weight is a weight of ≤200,000 g/mol,particularly preferably, ≤150,000 g/mol and especially preferably≤100,000.

Organic functional materials are frequently described by the propertiesof their frontier orbitals, which are described in greater detail below.Molecular orbitals, in particular also the highest occupied molecularorbital (HOMO) and the lowest unoccupied molecular orbital (LUMO), theirenergy levels and the energy of the lowest triplet state T₁ or of thelowest excited singlet state S₁ of the materials are determined viaquantum-chemical calculations. In order to calculate organic substanceswithout metals, firstly a geometry optimisation is carried out using the“Ground State/Semi-empirical/Default Spin/AM1/Charge 0/Spin Singlet”method. An energy calculation is subsequently carried out on the basisof the optimised geometry. The “TD-SCF/DFT/Default Spin/B3PW91” methodwith the “6-31G(d)” base set (charge 0, spin singlet) is used here. Formetal-containing compounds, the geometry is optimised via the “GroundState/Hartree-Fock/Default Spin/LanL2 MB/Charge 0/Spin Singlet” method.The energy calculation is carried out analogously to the above-describedmethod for the organic substances, with the difference that the“LanL2DZ” base set is used for the metal atom and the “6-31 G(d)” baseset is used for the ligands. The energy calculation gives the HOMOenergy level HEh or LUMO energy level LEh in hartree units. The HOMO andLUMO energy levels in electron volts calibrated with reference to cyclicvoltammetry measurements are determined therefrom as follows:

HOMO(eV)=((HEh*27.212)−0.9899)/1.1206

LUMO(eV)=((LEh*27.212)−2.0041)/1.385

For the purposes of this application, these values are to be regarded asHOMO and LUMO energy levels respectively of the materials.

The lowest triplet state T₁ is defined as the energy of the tripletstate having the lowest energy which arises from the quantum-chemicalcalculation described.

The lowest excited singlet state S₁ is defined as the energy of theexcited singlet state having the lowest energy which arises from thequantum-chemical calculation described.

The method described herein is independent of the software package usedand always gives the same results. Examples of frequently used programsfor this purpose are “Gaussian09 W” (Gaussian Inc.) and Q-Chem 4.1(Q-Chem, Inc.).

Materials having hole-injection properties, also called hole-injectionmaterials herein, simplify or facilitate the transfer of holes, i.e.positive charges, from the anode into an organic layer. In general, ahole-injection material has an HOMO level which is in the region of orabove the Fermi level of the anode.

Compounds having hole-transport properties, also called hole-transportmaterials herein, are capable of transporting holes, i.e. positivecharges, which are generally injected from the anode or an adjacentlayer, for example a hole-injection layer. A hole-transport materialgenerally has a high HOMO level of preferably at least −5.4 eV.Depending on the structure of an electronic device, it may also bepossible to employ a hole-transport material as hole-injection material.

The preferred compounds which have hole-injection and/or hole-transportproperties include, for example, triarylamine, benzidine,tetraaryl-para-phenylenediamine, triarylphosphine, phenothiazine,phenoxazine, dihydro-phenazine, thianthrene, dibenzo-para-dioxin,phenoxathiyne, carbazole, azulene, thiophene, pyrrole and furanderivatives and further O-, S- or N-containing heterocycles having ahigh HOMO (HOMO=highest occupied molecular orbital). Polymers such asPEDOT:PSS can also be used as compounds with hole-injection and/orhole-transport properties.

As compounds which have hole-injection and/or hole-transport properties,particular mention may be made of phenylenediamine derivatives (U.S.Pat. No. 3,615,404), arylamine derivatives (U.S. Pat. No. 3,567,450),amino-substituted chalcone derivatives (U.S. Pat. No. 3,526,501),styrylanthracene derivatives (JP-A-56-46234), polycyclic aromaticcompounds (EP 1009041), polyarylalkane derivatives (U.S. Pat. No.3,615,402), fluorenone derivatives (JP-A-54-110837), hydrazonederivatives (U.S. Pat. No. 3,717,462), acylhydrazones, stilbenederivatives (JP-A-61-210363), silazane derivatives (U.S. Pat. No.4,950,950), polysilanes (JP-A-2-204996), aniline copolymers(JP-A-2-282263), thiophene oligomers (JP Heisei 1 (1989) 211399),polythiophenes, poly(N-vinylcarbazole) (PVK), polypyrroles, polyanilinesand other electrically conducting macromolecules, porphyrin compounds(JP-A-63-2956965, U.S. Pat. No. 4,720,432), aromatic dimethylidene-typecompounds, carbazole compounds, such as, for example, CDBP, CBP, mCP,aromatic tertiary amine and styrylamine compounds (U.S. Pat. No.4,127,412), such as, for example, triphenylamines of the benzidine type,triphenylamines of the styrylamine type and triphenylamines of thediamine type. It is also possible to use arylamine dendrimers (JP Heisei8 (1996) 193191), monomeric triarylamines (U.S. Pat. No. 3,180,730),triarylamines containing one or more vinyl radicals and/or at least onefunctional group containing active hydrogen (U.S. Pat. Nos. 3,567,450and 3,658,520), or tetraaryldiamines (the two tertiary amine units areconnected via an aryl group). More triarylamino groups may also bepresent in the molecule. Phthalocyanine derivatives, naphthalocyaninederivatives, butadiene derivatives and quinoline derivatives, such as,for example, dipyrazino[2,3-f:2′,3′-h]-quinoxalinehexacarbonitrile, arealso suitable.

Preference is given to aromatic tertiary amines containing at least twotertiary amine units (US 2008/0102311 A1, U.S. Pat. Nos. 4,720,432 and5,061,569), such as, for example, NPD(α-NPD=4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl) (U.S. Pat. No.5,061,569), TPD 232(═N,N′-bis-(N,N′-diphenyl-4-aminophenyl)-N,N-diphenyl-4,4′-diamino-1,1′-biphenyl)or MTDATA (MTDATA orm-MTDATA=4,4′,4″-tris[3-methylphenyl)phenylamino]-triphenylamine)(JP-A-4-308688), TBDB (═N,N,N′,N′-tetra(4-biphenyl)-diaminobiphenylene),TAPC(=1,1-bis(4-di-p-tolylaminophenyl)cyclo-hexane), TAPPP(=1,1-bis(4-di-p-tolylaminophenyl)-3-phenylpropane), BDTAPVB(=1,4-bis[2-[4-[N,N-di(p-tolyl)amino]phenyl]vinyl]benzene), TTB(═N,N,N′,N′-tetra-p-tolyl-4,4′-diaminobiphenyl), TPD(=4,4′-bis[N-3-methylphenyl]-N-phenylamino)biphenyl),N,N,N′,N′-tetraphenyl-4,4″′-diamino-1,1′,4′,1″,4″,1″′-quaterphenyl,likewise tertiary amines containing carbazole units, such as, forexample, TCTA(=4-(9H-carbazol-9-yl)-N,N-bis[4-(9H-carbazol-9-yl)phenyl]benzenamine).Preference is likewise given to hexa-azatriphenylene compounds inaccordance with US 2007/0092755 A1 and phthalocyanine derivatives (forexample H₂Pc, CuPc (=copper phthalocyanine), CoPc, NiPc, ZnPc, PdPc,FePc, MnPc, ClAlPc, ClGaPc, ClInPc, CISnPc, Cl₂SiPc, (HO)AIPc, (HO)GaPc,VOPc, TiOPc, MoOPc, GaPc-O-GaPc).

Particular preference is given to the following triarylamine compoundsof the formulae (TA-1) to (TA-12), which are disclosed in the documentsEP 1162193 B1, EP 650 955 B1, Synth. Metals 1997, 91(1-3), 209, DE19646119 A1, WO 2006/122630 A1, EP 1 860 097 A1, EP 1834945 A1, JP08053397 A, U.S. Pat. No. 6,251,531 B1, US 2005/0221124, JP 08292586 A,U.S. Pat. No. 7,399,537 B2, US 2006/0061265 A1, EP 1 661 888 and WO2009/041635. The said compounds of the formulae (TA-1) to (TA-12) mayalso be substituted:

Further compounds which can be employed as hole-injection materials aredescribed in EP 0891121 A1 and EP 1029909 A1, injection layers ingeneral in US 2004/0174116 A1.

These arylamines and heterocycles which are generally employed ashole-injection and/or hole-transport materials preferably result in anHOMO in the polymer of greater than −5.8 eV (vs. vacuum level),particularly preferably greater than −5.5 eV.

Compounds which have electron-injection and/or electron-transportproperties are, for example, pyridine, pyrimidine, pyridazine, pyrazine,oxadiazole, quinoline, quinoxaline, anthracene, benzanthracene, pyrene,perylene, benzimidazole, triazine, ketone, phosphine oxide and phenazinederivatives, but also triarylboranes and further O-, S- or N-containingheterocycles having a low LUMO (LUMO=lowest unoccupied molecularorbital). Particularly suitable compounds for electron-transporting andelectron-injecting layers are metal chelates of 8-hydroxyquinoline (forexample LiQ, AlQ₃, GaQ₃, MgQ₂, ZnQ₂, InQ₃, ZrQ₄), BAlQ, Ga oxinoidcomplexes, 4-azaphenanthren-5-ol-Be complexes (U.S. Pat. No. 5,529,853A, cf. formula ET-1), butadiene derivatives (U.S. Pat. No. 4,356,429),heterocyclic optical brighteners (U.S. Pat. No. 4,539,507),benzimidazole derivatives (US 2007/0273272 A1), such as, for example,TPBI (U.S. Pat. No. 5,766,779, cf. formula ET-2), 1,3,5-triazines, forexample spirobifluorenyltriazine derivatives (for example in accordancewith DE 102008064200), pyrenes, anthracenes, tetracenes, fluorenes,spiro-fluorenes, dendrimers, tetracenes (for example rubrenederivatives), 1,10-phenanthroline derivatives (JP 2003-115387, JP2004-311184, JP-2001-267080, WO 02/043449), silacyclopentadienederivatives (EP 1480280, EP 1478032, EP 1469533), borane derivatives,such as, for example, triarylborane derivatives containing Si (US2007/0087219 A1, cf. formula ET-3), pyridine derivatives (JP2004-200162), phenanthrolines, especially 1,10-phenanthrolinederivatives, such as, for example, BCP and Bphen, also severalphenanthrolines connected via biphenyl or other aromatic groups(US-2007-0252517 A1) or phenanthrolines connected to anthracene (US2007-0122656 A1, cf. formulae ET-4 and ET-5).

Likewise suitable are heterocyclic organic compounds, such as, forexample, thiopyran dioxides, oxazoles, triazoles, imidazoles oroxadiazoles. Examples of the use of five-membered rings containing N,such as, for example, oxazoles, preferably 1,3,4-oxadiazoles, forexample compounds of the formulae ET-6, ET-7, ET-8 and ET-9, which aredisclose, inter alia, in US 2007/0273272 A1; thiazoles, oxadiazoles,thiadiazoles, triazoles, inter alia, see US 2008/0102311 A1 and Y. A.Levin, M. S. Skorobogatova, Khimiya Geterotsiklicheskikh Soedinenii 1967(2), 339-341, preferably compounds of the formula ET-10,silacyclopentadiene derivatives. Preferred compounds are the followingof the formulae (ET-6) to (ET-10):

It is also possible to employ organic compounds, such as derivatives offluorenone, fluorenylidenemethane, perylenetetracarbonic acid,anthra-quinonedimethane, diphenoquinone, anthrone andanthraquinone-diethylenediamine.

Preference is given to 2,9,10-substituted anthracenes (with 1- or2-naphthyl and 4- or 3-biphenyl) or molecules which contain twoanthracene units (US2008/0193796 A1, cf. formula ET-11). Also veryadvantageous is the connection of 9,10-substituted anthracene units tobenzimidazole derivatives (US 2006 147747 A and EP 1551206 A1, cf.formulae ET-12 and ET-13).

The compounds which are able to generate electron-injection and/orelectron-transport properties preferably result in an LUMO of less than−2.5 eV (vs. vacuum level), particularly preferably less than −2.7 eV.

n-Dopants herein are taken to mean reducing agents, i.e. electrondonors. Preferred examples of n-dopants are W(hpp)₄ and otherelectron-rich metal complexes in accordance with WO 2005/086251 A2, P═Ncompounds (for example WO 2012/175535 A1, WO 2012/175219 A1),naphthylenecarbo-diimides (for example WO 2012/168358 A1), fluorenes(for example WO 2012/031735 A1), free radicals and diradicals (forexample EP 1837926 A1, WO 2007/107306 A1), pyridines (for example EP2452946 A1, EP 2463927 A1), N-heterocyclic compounds (for example WO2009/000237 A1) and acridines as well as phenazines (for example US2007/145355 A1).

The present formulations may comprise emitters. The term emitter denotesa material which, after excitation, which can take place by transfer ofany type of energy, allows a radiative transition into a ground statewith emission of light. In general, two classes of emitter are known,namely fluorescent and phosphorescent emitters. The term fluorescentemitter denotes materials or compounds in which a radiative transitionfrom an excited singlet state into the ground state takes place. Theterm phosphorescent emitter preferably denotes luminescent materials orcompounds which contain transition metals.

Emitters are frequently also called dopants if the dopants cause theproperties described above in a system. A dopant in a system comprisinga matrix material and a dopant is taken to mean the component whoseproportion in the mixture is the smaller. Correspondingly, a matrixmaterial in a system comprising a matrix material and a dopant is takento mean the component whose proportion in the mixture is the greater.Accordingly, the term phosphorescent emitter can also be taken to mean,for example, phosphorescent dopants.

Compounds which are able to emit light include, inter alia, fluorescentemitters and phosphorescent emitters. These include, inter alia,compounds containing stilbene, stilbenamine, styrylamine, coumarine,rubrene, rhodamine, thiazole, thiadiazole, cyanine, thiophene,paraphenylene, perylene, phtalocyanine, porphyrin, ketone, quinoline,imine, anthracene and/or pyrene structures. Particular preference isgiven to compounds which are able to emit light from the triplet statewith high efficiency, even at room temperature, i.e. exhibitelectrophosphorescence instead of electro-fluorescence, which frequentlycauses an increase in the energy efficiency. Suitable for this purposeare firstly compounds which contain heavy atoms having an atomic numberof greater than 36. Preference is given to compounds which contain d- orf-transition metals which satisfy the above-mentioned condition.Particular preference is given here to corresponding compounds whichcontain elements from group 8 to 10 (Ru, Os, Rh, Ir, Pd, Pt). Suitablefunctional compounds here are, for example, various complexes, asdescribed, for example, in WO 02/068435 A1, WO 02/081488 A1, EP 1239526A2 and WO 2004/026886 A2.

Preferred compounds which can serve as fluorescent emitters aredescribed by way of example below. Preferred fluorescent emitters areselected from the class of the monostyrylamines, the distyrylamines, thetristyrylamines, the tetrastyrylamines, the styrylphosphines, the styrylethers and the arylamines.

A monostyrylamine is taken to mean a compound which contains onesubstituted or unsubstituted styryl group and at least one, preferablyaromatic, amine. A distyrylamine is taken to mean a compound whichcontains two substituted or unsubstituted styryl groups and at leastone, preferably aromatic, amine. A tristyrylamine is taken to mean acompound which contains three substituted or unsubstituted styryl groupsand at least one, preferably aromatic, amine. A tetrastyrylamine istaken to mean a compound which contains four substituted orunsubstituted styryl groups and at least one, preferably aromatic,amine. The styryl groups are particularly preferably stilbenes, whichmay also be further substituted. Corresponding phosphines and ethers aredefined analogously to the amines. An arylamine or an aromatic amine inthe sense of the present invention is taken to mean a compound whichcontains three substituted or unsubstituted aromatic or heteroaromaticring systems bonded directly to the nitrogen. At least one of thesearomatic or heteroaromatic ring systems is preferably a condensed ringsystem, preferably having at least 14 aromatic ring atoms. Preferredexamples thereof are aromatic anthracenamines, aromaticanthracene-diamines, aromatic pyrenamines, aromatic pyrenediamines,aromatic chrysenamines or aromatic chrysenediamines. An aromaticanthracen-amine is taken to mean a compound in which one diarylaminogroup is bonded directly to an anthracene group, preferably in the9-position. An aromatic anthracenediamine is taken to mean a compound inwhich two diarylamino groups are bonded directly to an anthracene group,preferably in the 2,6- or 9,10-position. Aromatic pyrenamines,pyrenediamines, chrysenamines and chrysenediamines are definedanalogously thereto, where the diarylamino groups are preferably bondedto the pyrene in the 1-position or in the 1,6-position.

Further preferred fluorescent emitters are selected fromindenofluorenamines or indenofluorenediamines, which are described,inter alia, in WO 2006/122630; benzoindenofluorenamines orbenzoindenofluorenediamines, which are described, inter alia, in WO2008/006449; and dibenzo-indenofluorenamines ordibenzoindenofluorenediamines, which are described, inter alia, in WO2007/140847.

Examples of compounds from the class of the styrylamines which can beemployed as fluorescent emitters are substituted or unsubstitutedtristilbenamines or the dopants described in WO 2006/000388, WO2006/058737, WO 2006/000389, WO 2007/065549 and WO 2007/115610.Distyryl-benzene and distyrylbiphenyl derivatives are described in U.S.Pat. No. 5,121,029. Further styrylamines can be found in US 2007/0122656A1.

Particularly preferred styrylamine compounds are the compounds of theformula EM-1 described in U.S. Pat. No. 7,250,532 B2 and the compoundsof the formula EM-2 described in DE 10 2005 058557 A1:

Particularly preferred triarylamine compounds are compounds of theformulae EM-3 to EM-15 disclosed in CN 1583691 A, JP 08/053397 A andU.S. Pat. No. 6,251,531 B1, EP 1957606 A1, US 2008/0113101 A1, US2006/210830 A, WO 2008/006449 and DE 102008035413 and derivativesthereof:

Further preferred compounds which can be employed as fluorescentemitters are selected from derivatives of naphthalene, anthracene,tetracene, benzanthracene, benzophenanthrene (DE 10 2009 005746),fluorene, fluoranthene, periflanthene, indenoperylene, phenanthrene,perylene (US 2007/0252517 A1), pyrene, chrysene, decacyclene, coronene,tetraphenylcyclopentadiene, pentaphenylcyclopentadiene, fluorene,spirofluorene, rubrene, coumarine (U.S. Pat. Nos. 4,769,292, 6,020,078,US 2007/0252517 A1), pyran, oxazole, benzoxazole, benzothiazole,benzimidazole, pyrazine, cinnamic acid esters, diketopyrrolopyrrole,acridone and quinacridone (US 2007/0252517 A1).

Of the anthracene compounds, particular preference is given to9,10-substituted anthracenes, such as, for example,9,10-diphenylanthracene and 9,10-bis(phenylethynyl)anthracene.1,4-Bis(9′-ethynylanthracenyl)-benzene is also a preferred dopant.

Preference is likewise given to derivatives of rubrene, coumarine,rhodamine, quinacridone, such as, for example, DMQA(═N,N′-dimethylquinacridone), dicyanomethylenepyran, such as, forexample, DCM(=4-(dicyano-ethylene)-6-(4-dimethylaminostyryl-2-methyl)-4H-pyran),thiopyran, polymethine, pyrylium and thiapyrylium salts, periflantheneand indenoperylene.

Blue fluorescent emitters are preferably polyaromatic compounds, suchas, for example, 9,10-di(2-naphthylanthracene) and other anthracenederivatives, derivatives of tetracene, xanthene, perylene, such as, forexample, 2,5,8,11-tetra-t-butylperylene, phenylene, for example4,4′-bis(9-ethyl-3-carbazovinylene)-1,1′-biphenyl, fluorene,fluoranthene, arylpyrenes (US 2006/0222886 A1), arylenevinylenes (U.S.Pat. Nos. 5,121,029, 5,130,603), bis-(azinyl)imine-boron compounds (US2007/0092753 A1), bis(azinyl)methene compounds and carbostyrylcompounds.

Further preferred blue fluorescent emitters are described in C. H. Chenet al.: “Recent developments in organic electroluminescent materials”Macro-mol. Symp. 125, (1997) 1-48 and “Recent progress of molecularorganic electroluminescent materials and devices” Mat. Sci. and Eng. R,39 (2002), 143-222.

Further preferred blue-fluorescent emitters are the hydrocarbonsdisclosed in DE 102008035413.

Preferred compounds which can serve as phosphorescent emitters aredescribed below by way of example.

Examples of phosphorescent emitters are revealed by WO 00/70655, WO01/41512, WO 02/02714, WO 02/15645, EP 1191613, EP 1191612, EP 1191614and WO 2005/033244. In general, all phosphorescent complexes as are usedin accordance with the prior art for phosphorescent OLEDs and as areknown to the person skilled in the art in the area of organicelectroluminescence are suitable, and the person skilled in the art willbe able to use further phosphorescent complexes without inventive step.

Phosphorescent metal complexes preferably contain Ir, Ru, Pd, Pt, Os orRe.

Preferred ligands are 2-phenylpyridine derivatives, 7,8-benzoquinolinederivatives, 2-(2-thienyl)pyridine derivatives, 2-(1-naphthyl)pyridinederivatives, 1-phenylisoquinoline derivatives, 3-phenylisoquinolinederivatives or 2-phenylquinoline derivatives. All these compounds may besubstituted, for example by fluoro, cyano and/or trifluoromethylsubstituents for blue. Auxiliary ligands are preferably acetylacetonateor picolinic acid.

In particular, complexes of Pt or Pd with tetradentate ligands of theformula EM-16 are suitable

The compounds of the formula EM-16 are described in greater detail in US2007/0087219 A1, where, for an explanation of the substituents andindices in the above formula, reference is made to this specificationfor disclosure purposes. Furthermore, Pt-porphyrin complexes having anenlarged ring system (US 2009/0061681 A1) and Ir complexes, for example2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphyrin-Pt(II),tetraphenyl-Pt(II) tetrabenzoporphyrin (US 2009/0061681 A1),cis-bis(2-phenylpyridinato-N,C^(2′))Pt(II),cis-bis(2-(2′-thienyl)pyridinato-N,C^(3′))Pt(II),cis-bis(2-(2′-thienyl)-quinolinato-N,C^(5′))Pt(II),(2-(4,6-difluorophenyl)pyridinato-N,C^(2′))Pt(II) (acetylacetonate), ortris(2-phenylpyridinato-N,C^(2′))Ir(III) (═Ir(ppy)₃, green),bis(2-phenylpyridinato-N,C²)Ir(III) (acetylacetonate) (═Ir(ppy)₂acetylacetonate, green, US 2001/0053462 A1, Baldo, Thompson et al.Nature 403, (2000), 750-753),bis(1-phenylisoquinolinato-N,C^(2′))(2-phenylpyridinato-N,C^(2′))-iridium(III),bis(2-phenylpyridinato-N,C^(2′))(1-phenylisoquinolinato-N,C^(2′))-iridium(III),bis(2-(2′-benzothienyl)pyridinato-N,C^(3′))iridium(II)(acetylacetonate),bis(2-(4′,6′-difluorophenyl)pyridinato-N,C^(2′))iridium(III)(picco-linate) (Flrpic, blue),bis(2-(4′,6′-difluorophenyl)pyridinato-N,C^(2′))Ir(III)(tetrakis(1-pyrazolyl)borate),tris(2-(biphenyl-3-yl)-4-tert-butylpyridine)-iridium(III),(ppz)₂Ir(5phdpym) (US 2009/0061681 A1), (45ooppz)₂-Ir(5phdpym) (US2009/0061681 A1), derivatives of 2-phenylpyridine-Ir complexes, such as,for example, PQIr (=iridium(III)bis(2-phenylquinolyl-N,C^(2′))acetylacetonate),tris(2-phenylisoquinolinato-N,C)Ir(III) (red),bis(2-(2′-benzo[4,5-a]thienyl)pyridinato-N,C³)Ir (acetylacetonate)([Btp₂Ir(acac)], red, Adachi et al. Appl. Phys. Lett. 78 (2001),1622-1624).

Likewise suitable are complexes of trivalent lanthanides, such as, forexample, Tb³⁺ and Eu³⁺ (J. Kido et al. Appl. Phys. Lett. 65 (1994),2124, Kido et al. Chem. Lett. 657, 1990, US 2007/0252517 A1), orphosphorescent complexes of Pt(II), Ir(I), Rh(I) with maleonitriledithiolate (Johnson et al., JACS 105, 1983, 1795), Re(I)tricarbonyl-diimine complexes (Wrighton, JACS 96, 1974, 998, interalia), Os(II) complexes with cyano ligands and bipyridyl orphenanthroline ligands (Ma et al., Synth. Metals 94, 1998, 245).

Further phosphorescent emitters having tridentate ligands are describedin U.S. Pat. No. 6,824,895 and U.S. Ser. No. 10/729,238. Red-emittingphosphorescent complexes are found in U.S. Pat. Nos. 6,835,469 and6,830,828.

Particularly preferred compounds which are used as phosphorescentdopants are, inter alia, the compounds of the formula EM-17 described,inter alia, in US 2001/0053462 A1 and Inorg. Chem. 2001, 40(7),1704-1711, JACS 2001, 123(18), 4304-4312, and derivatives thereof.

Derivatives are described in U.S. Pat. No. 7,378,162 B2, U.S. Pat. No.6,835,469 B2 and JP 2003/253145 A.

Furthermore, the compounds of the formulae EM-18 to EM-21 described inU.S. Pat. No. 7,238,437 B2, US 2009/008607 A1 and EP 1348711, andderivatives thereof, can be employed as emitters.

Quantum dots can likewise be employed as emitters, these materials beingdisclosed in detail in WO 2011/076314 A1.

Compounds which are employed as host materials, in particular togetherwith emitting compounds, include materials from various classes ofsubstance.

Host materials generally have larger band gaps between HOMO and LUMOthan the emitter materials employed. In addition, preferred hostmaterials exhibit properties of either a hole- or electron-transportmaterial. Furthermore, host materials can have both electron- andhole-transport properties.

Host materials are in some cases also called matrix material, inparticular if the host material is employed in combination with aphosphorescent emitter in an OLED.

Preferred host materials or co-host materials, which are employed, inparticular, together with fluorescent dopants, are selected from theclasses of the oligoarylenes (for example2,2′,7,7′-tetraphenylspirobifluorene in accordance with EP 676461 ordinaphthylanthracene), in particular the oligoarylenes containingcondensed aromatic groups, such as, for example, anthracene,benzanthracene, benzophenanthrene (DE 10 2009 005746, WO 2009/069566),phenanthrene, tetracene, coronene, chrysene, fluorene, spirofluorene,perylene, phthaloperylene, naphthaloperylene, decacyclene, rubrene, theoligoarylenevinylenes (for exampleDPVBi=4,4′-bis(2,2-diphenylethenyl)-1,1′-biphenyl or spiro-DPVBi inaccordance with EP 676461), the polypodal metal complexes (for examplein accordance with WO 04/081017), in particular metal complexes of8-hydroxyquinoline, for example AlQ₃ (=aluminium(III)tris(8-hydroxyquinoline)) orbis(2-methyl-8-quinolinolato)-4-(phenylphenolinolato)aluminium, alsowith imidazole chelate (US 2007/0092753 A1) and the quinoline-metalcomplexes, amino-quinoline-metal complexes, benzoquinoline-metalcomplexes, the hole-conducting compounds (for example in accordance withWO 2004/058911), the electron-conducting compounds, in particularketones, phosphine oxides, sulfoxides, etc. (for example in accordancewith WO 2005/084081 and WO 2005/084082), the atropisomers (for examplein accordance with WO 2006/048268), the boronic acid derivatives (forexample in accordance with WO 2006/117052) or the benzanthracenes (forexample in accordance with WO 2008/145239).

Particularly preferred compounds which can serve as host materials orco-host materials are selected from the classes of the oligoarylenes,comprising anthracene, benzanthracene and/or pyrene, or atropisomers ofthese compounds. An oligoarylene in the sense of the present inventionis intended to be taken to mean a compound in which at least three arylor arylene groups are bonded to one another.

Preferred host materials are selected, in particular, from compounds ofthe formula (H-1),

Ar⁴—(Ar⁵)_(p)—Ar⁶  (H-1)

where Ar⁴, Ar⁵, Ar⁶ are on each occurrence, identically or differently,an aryl or heteroaryl group having 5 to 30 aromatic ring atoms, whichmay optionally be substituted, and p represents an integer in the rangefrom 1 to 5; the sum of the π electrons in Ar⁴, Ar⁵ and Ar⁶ is at least30 if p=1 and at least 36 if p=2 and at least 42 if p=3.

In the compounds of the formula (H-1), the group Ar⁵ particularlypreferably stands for anthracene, and the groups Ar⁴ and Ar⁶ are bondedin the 9- and 10-position, where these groups may optionally besubstituted. Very particularly preferably, at least one of the groupsAr⁴ and/or Ar⁶ is a condensed aryl group selected from 1- or 2-naphthyl,2-, 3- or 9-phenanthrenyl or 2-, 3-, 4-, 5-, 6- or 7-benzanthracenyl.Anthracene-based compounds are described in US 2007/0092753 A1 and US2007/0252517 A1, for example2-(4-methylphenyl)-9,10-di-(2-naphthyl)anthracene,9-(2-naphthyl)-10-(1,1′-biphenyl)anthracene and9,10-bis[4-(2,2-diphenylethenyl)phenyl]anthracene,9,10-diphenylanthracene, 9,10-bis(phenylethynyl)anthracene and1,4-bis(9′-ethynylanthracenyl)benzene. Preference is also given tocompounds containing two anthracene units (US 2008/0193796 A1), forexample 10,10′-bis[1,1′,4′,1″ ]terphenyl-2-yl-9,9′-bisanthracenyl.

Further preferred compounds are derivatives of arylamine, styrylamine,fluorescein, diphenylbutadiene, tetraphenylbutadiene, cyclopentadiene,tetraphenylcyclopentadiene, pentaphenylcyclopentadiene, coumarine,oxadiazole, bisbenzoxazoline, oxazole, pyridine, pyrazine, imine,benzothiazole, benzoxazole, benzimidazole (US 2007/0092753 A1), forexample 2,2′,2″-(1,3,5-phenylene)tris[1-phenyl-1H-benzimidazole],aldazine, stilbene, styrylarylene derivatives, for example9,10-bis[4-(2,2-diphenyl-ethenyl)phenyl]anthracene, and distyrylarylenederivatives (U.S. Pat. No. 5,121,029), diphenylethylene,vinylanthracene, diaminocarbazole, pyran, thiopyran,diketopyrrolopyrrole, polymethine, cinnamic acid esters and fluorescentdyes.

Particular preference is given to derivatives of arylamine andstyrylamine, for example TNB(=4,4′-bis[N-(1-naphthyl)-N-(2-naphthyl)amino]biphenyl). Metal-oxinoidcomplexes, such as LiQ or AlQ₃, can be used as co-hosts.

Preferred compounds with oligoarylene as matrix are disclosed in US2003/0027016 A1, U.S. Pat. No. 7,326,371 B2, US 2006/043858 A, WO2007/114358, WO 2008/145239, JP 3148176 B2, EP 1009044, US 2004/018383,WO 2005/061656 A1, EP 0681019B1, WO 2004/013073A1, U.S. Pat. No.5,077,142, WO 2007/065678 and DE 102009005746, where particularlypreferred compounds are described by the formulae H-2 to H-8.

Furthermore, compounds which can be employed as host or matrix includematerials which are employed together with phosphorescent emitters.

These compounds, which can also be employed as structural elements inpolymers, include CBP (N,N-biscarbazolylbiphenyl), carbazole derivatives(for example in accordance with WO 2005/039246, US 2005/0069729, JP2004/288381, EP 1205527 or WO 2008/086851), azacarbazoles (for examplein accordance with EP 1617710, EP 1617711, EP 1731584 or JP2005/347160), ketones (for example in accordance with WO 2004/093207 orin accordance with DE 102008033943), phosphine oxides, sulfoxides andsulfones (for example in accordance with WO 2005/003253),oligophenylenes, aromatic amines (for example in accordance with US2005/0069729), bipolar matrix materials (for example in accordance withWO 2007/137725), silanes (for example in accordance with WO2005/111172), 9,9-diarylfluorene derivatives (for example in accordancewith DE 102008017591), azaboroles or boronic esters (for example inaccordance with WO 2006/117052), triazine derivatives (for example inaccordance with DE 102008036982), indolocarbazole derivatives (forexample in accordance with WO 2007/063754 or WO 2008/056746),indenocarbazole derivatives (for example in accordance with DE102009023155 and DE 102009031021), diazaphosphole derivatives (forexample in accordance with DE 102009022858), triazole derivatives,oxazoles and oxazole derivatives, imidazole derivatives, polyarylalkanederivatives, pyrazoline derivatives, pyrazolone derivatives,distyrylpyrazine derivatives, thiopyran dioxide derivatives,phenylenediamine derivatives, tertiary aromatic amines, styrylamines,amino-substituted chalcone derivatives, indoles, hydrazone derivatives,stilbene derivatives, silazane derivatives, aromatic dimethylidenecompounds, carbodiimide derivatives, metal complexes of8-hydroxyquinoline derivatives, such as, for example, AlQ₃, which mayalso contain triarylaminophenol ligands (US 2007/0134514 A1), metalcomplex/poly-silane compounds, and thiophene, benzothiophene anddibenzothiophene derivatives.

Examples of preferred carbazole derivatives are mCP(=1,3-N,N-di-carbazolylbenzene (=9,9′-(1,3-phenylene)bis-9H-carbazole))(formula H-9), CDBP(=9,9′-(2,2′-dimethyl[1,1′-biphenyl]-4,4′-diyl)bis-9H-carbazole),1,3-bis(N,N′-dicarbazolyl)benzene (=1,3-bis(carbazol-9-yl)benzene), PVK(polyvinylcarbazole), 3,5-di(9H-carbazol-9-yl)biphenyl and CMTTP(formula H-10). Particularly referred compounds are disclosed in US2007/0128467 A1 and US 2005/0249976 A1 (formulae H-11 and H-13).

Preferred tetraaryl-Si compounds are disclosed, for example, in US2004/0209115, US 2004/0209116, US 2007/0087219 A1 and in H. Gilman, E.A.Zuech, Chemistry & Industry (London, United Kingdom), 1960, 120.

Particularly preferred tetraaryl-Si compounds are described by theformulae H-14 to H-20.

Particularly preferred compounds from group 4 for the preparation of thematrix for phosphorescent dopants are disclosed, inter alia, in DE102009022858, DE 102009023155, EP 652273 B1, WO 2007/063754 and WO2008/056746, where particularly preferred compounds are described by theformulae H-21 to H-24.

With respect to the functional compounds which can be employed inaccordance with the invention and which can serve as host material,especial preference is given to substances which contain at least onenitrogen atom. These preferably include aromatic amines, triazinederivatives and carbazole derivatives. Thus, carbazole derivatives inparticular exhibit surprisingly high efficiency. Triazine derivativesresult in unexpectedly long lifetimes of the electronic devices.

It may also be preferred to employ a plurality of different matrixmaterials as a mixture, in particular at least one electron-conductingmatrix material and at least one hole-conducting matrix material.Preference is likewise given to the use of a mixture of acharge-transporting matrix material and an electrically inert matrixmaterial which is not in involved in the charge transport to asignificant extent, if at all, as described, for example, in WO2010/108579.

It is furthermore possible to employ compounds which improve thetransition from the singlet state to the triplet state and which,employed in support of the functional compounds having emitterproperties, improve the phosphorescence properties of these compounds.Suitable for this purpose are, in particular, carbazole and bridgedcarbazole dimer units, as described, for example, in WO 2004/070772 A2and WO 2004/113468 A1. Also suitable for this purpose are ketones,phosphine oxides, sulfoxides, sulfones, silane derivatives and similarcompounds, as described, for example, in WO 2005/040302 A1.

Furthermore, the formulations may comprise a wide-band-gap material asfunctional material. Wide-band-gap material is taken to mean a materialin the sense of the disclosure content of U.S. Pat. No. 7,294,849. Thesesystems exhibit particularly advantageous performance data inelectroluminescent devices. The compound employed as wide-band-gapmaterial can preferably have a band gap of 2.5 eV or more, preferably3.0 eV or more, particularly preferably 3.5 eV or more. The band gap canbe calculated, inter alia, by means of the energy levels of the highestoccupied molecular orbital (HOMO) and the lowest unoccupied molecularorbital (LUMO).

Furthermore, the formulations may comprise a hole-blocking material(HBM) as functional material. A hole-blocking material denotes amaterial which prevents or minimises the transmission of holes (positivecharges) in a multilayer system, in particular if this material isarranged in the form of a layer adjacent to an emission layer or ahole-conducting layer. In general, a hole-blocking material has a lowerHOMO level than the hole-transport material in the adjacent layer.Hole-blocking layers are frequently arranged between the light-emittinglayer and the electron-transport layer in OLEDs.

It is basically possible to employ any known hole-blocking material. Inaddition to other hole-blocking materials described elsewhere in thepresent application, advantageous hole-blocking materials are metalcomplexes (US 2003/0068528), such as, for example,bis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminium(III) (BAlQ).Fac-tris(1-phenylpyrazolato-N,C2)-iridium(III) (Ir(ppz)₃) is likewiseemployed for this purpose (US 2003/0175553 A1). Phenanthrolinederivatives, such as, for example, BCP, or phthalimides, such as, forexample, TMPP, can likewise be employed.

Furthermore, advantageous hole-blocking materials are described in WO00/70655 A2, WO 01/41512 and WO 01/93642 A1.

Furthermore, the formulations may comprise an electron-blocking material(EBM) as functional material. An electron-blocking material denotes amaterial which prevents or minimises the transmission of electrons in amultilayer system, in particular if this material is arranged in theform of a layer adjacent to an emission layer or an electron-conductinglayer. In general, an electron-blocking material has a higher LUMO levelthan the electron-transport material in the adjacent layer.

It is basically possible to employ any known electron-blocking material.In addition to other electron-blocking materials described elsewhere inthe present application, advantageous electron-blocking materials aretransition-metal complexes, such as, for example, Ir(ppz)₃ (US2003/0175553).

The electron-blocking material can preferably be selected from amines,triarylamines and derivatives thereof.

Furthermore, the functional compounds which can be employed as organicfunctional materials in the formulations preferably have, if they arelow-molecular-weight compounds, a molecular weight of <3,000 g/mol,particularly preferably ≤2,000 g/mol and especially preferably ≤1,800g/mol.

Of particular interest are furthermore functional compounds which aredistinguished by a high glass-transition temperature. In thisconnection, particularly preferred functional compounds which can beemployed as organic functional material in the formulations are thosewhich have a glass-transition temperature of ≥70° C., preferably ≥100°C., particularly preferably ≥125° C. and especially preferably ≥150° C.,determined in accordance with DIN 51005.

The formulations may also comprise polymers as organic functionalmaterials. The compounds described above as organic functionalmaterials, which frequently have a relatively low molecular weight, canalso be mixed with a polymer. It is likewise possible to incorporatethese compounds covalently into a polymer. This is possible, inparticular, with compounds which are substituted by reactive leavinggroups, such as bromine, iodine, chlorine, boronic acid or boronic acidester, or by reactive, polymerisable groups, such as olefins oroxetanes. These can be used as monomers for the production ofcorresponding oligomers, dendrimers or polymers. The oligomerisation orpolymerisation here preferably takes place via the halogen functionalityor the boronic acid functionality or via the polymerisable group. It isfurthermore possible to crosslink the polymers via groups of this type.The compounds and polymers according to the invention can be employed ascrosslinked or uncrosslinked layer.

Polymers which can be employed as organic functional materialsfrequently contain units or structural elements which have beendescribed in the con-text of the compounds described above, inter aliathose as disclosed and extensively listed in WO 02/077060 A1, in WO2005/014689 A2 and in WO 2011/076314 A1. These are incorporated into thepresent application by way of reference. The functional materials canoriginate, for example, from the following classes:

-   Group 1: structural elements which are able to generate    hole-injection and/or hole-transport properties;-   Group 2: structural elements which are able to generate    electron-injection and/or electron-transport properties;-   Group 3: structural elements which combine the properties described    in relation to groups 1 and 2;-   Group 4: structural elements which have light-emitting properties,    in particular phosphorescent groups;-   Group 5: structural elements which improve the transition from the    so-called singlet state to the triplet state;-   Group 6: structural elements which influence the morphology or also    the emission colour of the resultant polymers;-   Group 7: structural elements which are typically used as backbone.

The structural elements here may also have various functions, so that aclear assignment need not be advantageous. For example, a structuralelement of group 1 may likewise serve as backbone.

The polymer having hole-transport or hole-injection properties employedas organic functional material, containing structural elements fromgroup 1, may preferably contain units which correspond to thehole-transport or hole-injection materials described above.

Further preferred structural elements of group 1 are, for example,triarylamine, benzidine, tetraaryl-para-phenylenediamine, carbazole,azulene, thiophene, pyrrole and furan derivatives and further O-, S- orN-containing heterocycles having a high HOMO. These arylamines andheterocycles preferably have an HOMO of above −5.8 eV (against vacuumlevel), particularly preferably above −5.5 eV.

Preference is given, inter alia, to polymers having hole-transport orhole-injection properties, containing at least one of the followingrecurring units of the formula HTP-1:

in which the symbols have the following meaning:

-   Ar¹ is, in each case identically or differently for different    recurring units, a single bond or a monocyclic or polycyclic aryl    group, which may optionally be substituted;-   Ar² is, in each case identically or differently for different    recurring units, a monocyclic or polycyclic aryl group, which may    optionally be substituted;-   Ar³ is, in each case identically or differently for different    recurring units, a monocyclic or polycyclic aryl group, which may    optionally be substituted;-   m is 1, 2 or 3.

Particular preference is given to recurring units of the formula HTP-1which are selected from the group consisting of units of the formulaeHTP-1A to HTP-1C:

in which the symbols have the following meaning:

-   R^(a) is on each occurrence, identically or differently, H, a    substituted or unsubstituted aromatic or heteroaromatic group, an    alkyl, cycloalkyl, alkoxy, aralkyl, aryloxy, arylthio,    alkoxycarbonyl, silyl or carboxyl group, a halogen atom, a cyano    group, a nitro group or a hydroxyl group;-   r is 0, 1, 2, 3 or 4, and-   s is 0, 1, 2, 3, 4 or 5.

Preference is given, inter alia, to polymers having hole-transport orhole-injection properties, containing at least one of the followingrecurring units of the formula HTP-2:

-(T¹)_(c)—(Ar⁷)_(d)-(T²)_(e)—(Ar⁸)_(f)—  HTP-2

in which the symbols have the following meaning:T¹ and T² are selected independently from thiophene, selenophene,thieno-[2,3-b]thiophene, thieno[3,2-b]thiophene, dithienothiophene,pyrrole and aniline, where these groups may be substituted by one ormore radicals R^(b);R^(b) is selected independently on each occurrence from halogen, —CN,—NC, —NCO, —NCS, —OCN, —SCN, —C(═O)NR⁰R⁰⁰, —C(═O)X, —C(═O)R⁰, —NH₂,—NR⁰R⁰⁰, —SH, —SR⁰, —SO₃H, —SO₂R⁰, —OH, —NO₂, —CF₃, —SF₅, an optionallysubstituted silyl, carbyl or hydrocarbyl group having 1 to 40 carbonatoms, which may optionally be substituted and may optionally containone or more heteroatoms;R⁰ and R⁰⁰ are each independently H or an optionally substituted carbylor hydrocarbyl group having 1 to 40 carbon atoms, which may optionallybe substituted and may optionally contain one or more heteroatoms;Ar⁷ and Ar⁸ represent, independently of one another, a monocyclic orpolycyclic aryl or heteroaryl group, which may optionally be substitutedand may optionally be bonded to the 2,3-position of one or both adjacentthiophene or selenophene groups;c and e are, independently of one another, 0, 1, 2, 3 or 4, where1<c+e≤6;d and f are, independently of one another, 0, 1, 2, 3 or 4.

Preferred examples of polymers having hole-transport or hole-injectionproperties are described, inter alia, in WO 2007/131582 A1 and WO2008/009343A1.

The polymer having electron-injection and/or electron-transportproperties employed as organic functional material, containingstructural elements from group 2, may preferably contain units whichcorrespond to the electron-injection and/or electron-transport materialsdescribed above.

Further preferred structural elements of group 2 which haveelectron-injection and/or electron-transport properties are derived, forexample, from pyridine, pyrimidine, pyridazine, pyrazine, oxadiazole,quinoline, quinoxaline and phenazine groups, but also triarylboranegroups or further O-, S- or N-containing heterocycles having a low LUMOlevel. These structural elements of group 2 preferably have an LUMO ofbelow −2.7 eV (against vacuum level), particularly preferably below −2.8eV.

The organic functional material can preferably be a polymer whichcontains structural elements from group 3, where structural elementswhich improve the hole and electron mobility (i.e. structural elementsfrom groups 1 and 2) are connected directly to one another. Some ofthese structural elements can serve as emitters here, where the emissioncolours may be shifted, for example, into the green, red or yellow.Their use is therefore advantageous, for example, for the generation ofother emission colours or a broad-band emission by polymers whichoriginally emit in blue.

The polymer having light-emitting properties employed as organicfunctional material, containing structural elements from group 4, maypreferably contain units which correspond to the emitter materialsdescribed above. Preference is given here to polymers containingphosphorescent groups, in particular the emitting metal complexesdescribed above which contain corresponding units containing elementsfrom groups 8 to 10 (Ru, Os, Rh, Ir, Pd, Pt).

The polymer employed as organic functional material containing units ofgroup 5 which improve the transition from the so-called singlet state tothe triplet state can preferably be employed in support ofphosphorescent compounds, preferably the polymers containing structuralelements of group 4 described above. A polymeric triplet matrix can beused here.

Suitable for this purpose are, in particular, carbazole and connectedcarbazole dimer units, as described, for example, in DE 10304819 A1 andDE 10328627 A1. Also suitable for this purpose are ketone, phosphineoxide, sulfoxide, sulfone and silane derivatives and similar compounds,as described, for example, in DE 10349033 A1. Furthermore, preferredstructural units can be derived from compounds which have been describedabove in connection with the matrix materials employed together withphosphorescent compounds.

The further organic functional material is preferably a polymercontaining units of group 6 which influence the morphology and/or theemission colour of the polymers. Besides the polymers mentioned above,these are those which have at least one further aromatic or anotherconjugated structure which do not count amongst the above-mentionedgroups. These groups accordingly have only little or no effect on thecharge-carrier mobilities, the non-organometallic complexes or thesinglet-triplet transition.

The polymers may also include cross-linkable groups such as styrene,benzocyclobutene, epoxide and oxetane moieties.

Structural units of this type are able to influence the morphologyand/or the emission colour of the resultant polymers. Depending on thestructural unit, these polymers can therefore also be used as emitters.

In the case of fluorescent OLEDs, preference is therefore given toaromatic structural elements having 6 to 40 C atoms or also tolan,stilbene or bisstyrylarylene derivative units, each of which may besubstituted by one or more radicals. Particular preference is given hereto the use of groups derived from 1,4-phenylene, 1,4-naphthylene, 1,4-or 9,10-anthrylene, 1,6-, 2,7- or 4,9-pyrenylene, 3,9- or3,10-perylenylene, 4,4′-biphenylene, 4,4″-terphenylylene,4,4′-bi-1,1′-naphthylylene, 4,4′-tolanylene, 4,4′-stilbenylene or4,4″-bisstyrylarylene derivatives.

The polymer employed as organic functional material preferably containsunits of group 7, which preferably contain aromatic structures having 6to 40 C atoms which are frequently used as backbone.

These include, inter alia, 4,5-dihydropyrene derivatives,4,5,9,10-tetra-hydropyrene derivatives, fluorene derivatives, which aredisclosed, for example, in U.S. Pat. No. 5,962,631, WO 2006/052457 A2and WO 2006/118345A1, 9,9-spirobifluorene derivatives, which aredisclosed, for example, in WO 2003/020790 A1, 9,10-phenanthrenederivatives, which are disclosed, for example, in WO 2005/104264 A1,9,10-dihydrophenanthrene derivatives, which are disclosed, for example,in WO 2005/014689 A2, 5,7-dihydrodibenzoxepine derivatives and cis- andtrans-indenofluorene derivatives, which are disclosed, for example, inWO 2004/041901 A1 and WO 2004/113412 A2, and binaphthylene derivatives,which are disclosed, for example, in WO 2006/063852 A1, and furtherunits which are disclosed, for example, in WO 2005/056633A1, EP1344788A1, WO 2007/043495A1, WO 2005/033174 A1, WO 2003/099901 A1 and DE102006003710.

Particular preference is given to structural units of group 7 which areselected from fluorene derivatives, which are disclosed, for example, inU.S. Pat. No. 5,962,631, WO 2006/052457 A2 and WO 2006/118345 A1,spirobifluorene derivatives, which are disclosed, for example, in WO2003/020790 A1, benzofluorene, dibenzofluorene, benzothiophene anddibenzofluorene groups and derivatives thereof, which are disclosed, forexample, in WO 2005/056633 A1, EP 1344788 A1 and WO 2007/043495 A1.

Especially preferred structural elements of group 7 are represented bythe general formula PB-1:

in which the symbols and indices have the following meanings:A, B and B′ are each, also for different recurring units, identically ordifferently, a divalent group, which is preferably selected from—CR^(c)R^(d)—, —NR^(c)—, —PR^(c)—, —O—, —S—, —SO—, —SO₂—, —CO—, —CS—,—CSe—, —P(═O)R^(c)—, —P(═S)R^(c)- and —SiR^(c)R^(d)—;R^(c) and R^(d) are selected on each occurrence, independently, from H,halogen, —CN, —NC, —NCO, —NCS, —OCN, —SCN, —C(═O)NR⁰R⁰⁰, —C(═O)X,—C(═O)R⁰, —NH₂, —NR⁰R⁰⁰, —SH, —SR⁰, —SO₃H, —SO₂R⁰, —OH, —NO₂, —CF₃,—SF₅, an optionally substituted silyl, carbyl or hydrocarbyl grouphaving 1 to 40 carbon atoms, which may optionally be substituted and mayoptionally contain one or more heteroatoms, where the groups R^(c) andR^(d) may optionally form a spiro group with a fluorene radical to whichthey are bonded;X is halogen;R⁰ and R⁰⁰ are each, independently, H or an optionally substitutedcarbyl or hydrocarbyl group having 1 to 40 carbon atoms, which mayoptionally be substituted and may optionally contain one or moreheteroatoms;g is in each case, independently, 0 or 1 and h is in each case,independently, 0 or 1, where the sum of g and h in a sub-unit ispreferably 1;m is an integer ≥1;Ar¹ and Ar² represent, independently of one another, a monocyclic orpolycyclic aryl or heteroaryl group, which may optionally be substitutedand may optionally be bonded to the 7,8-position or the 8,9-position ofan indenofluorene group;a and b are, independently of one another, 0 or 1.

If the groups R^(c) and R^(d) form a spiro group with the fluorene groupto which these groups are bonded, this group preferably represents aspirobifluorene.

Particular preference is given to recurring units of the formula PB-1which are selected from the group consisting of units of the formulaePB-1A to PB-1E:

where R^(c) has the meaning described above for formula PB-1, r is 0, 1,2, 3 or 4, and R^(e) has the same meaning as the radical R^(c).R^(e) is preferably —F, —Cl, —Br, —I, —CN, —NO₂, —NCO, —NCS, —OCN, —SCN,—C(═O)NR⁰R⁰⁰, —C(═O)X, —C(═O)R⁰, —NR⁰R⁰⁰, an optionally substitutedsilyl, aryl or heteroaryl group having 4 to 40, preferably 6 to 20, Catoms, or a straight-chain, branched or cyclic alkyl, alkoxy,alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxygroup having 1 to 20, preferably 1 to 12, C atoms, where one or morehydrogen atoms may optionally be substituted by F or Cl, and the groupsR⁰, R⁰⁰ and X have the meaning described above for formula PB-1.

Particular preference is given to recurring units of the formula PB-1which are selected from the group consisting of units of the formulaePB-1F to PB-1I:

in which the symbols have the following meaning:L is H, halogen or an optionally fluorinated, linear or branched alkylor alkoxy group having 1 to 12 C atoms and preferably stands for H, F,methyl, i-propyl, t-butyl, n-pentoxy or trifluoromethyl; andL′ is an optionally fluorinated, linear or branched alkyl or alkoxygroup having 1 to 12 C atoms and preferably stands for n-octyl orn-octyloxy.

For carrying out the present invention, preference is given to polymerswhich contain more than one of the structural elements of groups 1 to 7described above. It may furthermore be provided that the polymerspreferably contain more than one of the structural elements from onegroup described above, i.e. comprise mixtures of structural elementsselected from one group.

Particular preference is given, in particular, to polymers which,besides at least one structural element which has light-emittingproperties (group 4), preferably at least one phosphorescent group,additionally contain at least one further structural element of groups 1to 3, 5 or 6 described above, where these are preferably selected fromgroups 1 to 3.

The proportion of the various classes of groups, if present in thepolymer, can be in broad ranges, where these are known to the personskilled in the art. Surprising advantages can be achieved if theproportion of one class present in a polymer, which is in each caseselected from the structural elements of groups 1 to 7 described above,is preferably in each case ≥5 mol %, particularly preferably in eachcase ≥10 mol %.

The preparation of white-emitting copolymers is described in detail,inter alia, in DE 10343606 A1.

In order to improve the solubility, the polymers may containcorresponding groups. It may preferably be provided that the polymerscontain substituents, so that on average at least 2 non-aromatic carbonatoms, particularly preferably at least 4 and especially preferably atleast 8 non-aromatic carbon atoms are present per recurring unit, wherethe average relates to the number average. Individual carbon atoms heremay be replaced, for example, by O or S. However, it is possible for acertain proportion, optionally all recurring units, to contain nosubstituents which contain non-aromatic carbon atoms. Short-chainsubstituents are preferred here, since long-chain substituents can haveadverse effects on layers which can be obtained using organic functionalmaterials. The substituents preferably contain at most 12 carbon atoms,preferably at most 8 carbon atoms and particularly preferably at most 6carbon atoms in a linear chain.

The polymer employed in accordance with the invention as organicfunctional material can be a random, alternating or regioregularcopolymer, a block copolymer or a combination of these copolymer forms.

In a further embodiment, the polymer employed as organic functionalmaterial can be a non-conjugated polymer having side chains, where thisembodiment is particularly important for phosphorescent OLEDs based onpolymers. In general, phosphorescent polymers can be obtained byfree-radical copolymerisation of vinyl compounds, where these vinylcompounds contain at least one unit having a phosphorescent emitterand/or at least one charge-transport unit, as is disclosed, inter alia,in U.S. Pat. No. 7,250,226 B2. Further phosphorescent polymers aredescribed, inter alia, in JP 2007/211243 A2, JP 2007/197574 A2, U.S.Pat. No. 7,250,226 B2 and JP 2007/059939 A.

In a further preferred embodiment, the non-conjugated polymers containbackbone units, which are connected to one another by spacer units.Examples of such triplet emitters which are based on non-conjugatedpolymers based on backbone units are disclosed, for example, in DE102009023154.

In a further preferred embodiment, the non-conjugated polymer can bedesigned as fluorescent emitter. Preferred fluorescent emitters whichare based on non-conjugated polymers having side chains containanthracene or benzanthracene groups or derivatives of these groups inthe side chain, where these polymers are disclosed, for example, in JP2005/108556, JP 2005/285661 and JP 2003/338375.

These polymers can frequently be employed as electron- or hole-transportmaterials, where these polymers are preferably designed asnon-conjugated polymers.

Furthermore, the functional compounds employed as organic functionalmaterials in the formulations preferably have, in the case of polymericcompounds, a molecular weight M_(W) of 10,000 g/mol, particularlypreferably 20,000 g/mol and especially preferably 50,000 g/mol.

The molecular weight M_(w) of the polymers here is preferably in therange from 10,000 to 2,000,000 g/mol, particularly preferably in therange from 20,000 to 1,000,000 g/mol and very particularly preferably inthe range from 50,000 to 300,000 g/mol. The molecular weight M_(w) isdetermined by means of GPC(=gel permeation chromatography) against aninternal polystyrene standard.

The publications cited above for description of the functional compoundsare incorporated into the present application by way of reference fordisclosure purposes.

It is preferred that the formulation of the present invention ischaracterized in that the organic semiconductor is a polymeric compound,a non-polymeric compound or a blend of a polymeric compound and anon-polymeric compound.

The formulations according to the invention may comprise all organicfunctional materials which are necessary for the production of therespective functional layer of the electronic device. If, for example, ahole-transport, hole-injection, electron-transport or electron-injectionlayer is built up precisely from one functional compound, theformulation comprises precisely this compound as organic functionalmaterial. If an emission layer comprises, for example, an emitter incombination with a matrix or host material, the formulation comprises,as organic functional material, precisely the mixture of emitter andmatrix or host material, as described in greater detail elsewhere in thepresent application.

Besides the said components, the formulation according to the inventionmay comprise further additives and processing assistants. These include,inter alia, surface-active substances (surfactants), lubricants andgreases, additives which modify the viscosity, additives which increasethe conductivity, dispersants, hydrophobicising agents, adhesionpromoters, flow improvers, antifoams, deaerating agents, diluents, whichmay be reactive or unreactive, fillers, assistants, processingassistants, dyes, pigments, stabilisers, sensitisers, nanoparticles andinhibitors.

The present invention furthermore relates to a process for thepreparation of a formulation according to the invention, wherein the atleast one ester solvent, the optional further solvent and the at leastone organic functional material, which can be employed for theproduction of functional layers of organic electronic devices, aremixed.

A formulation in accordance with the present invention can be employedfor the production of a layer or multilayered structure in which theorganic functional materials are present in layers, as are required forthe production of preferred electronic or opto-electronic components,such as OLEDs.

The formulation of the present invention can preferably be employed forthe formation of functional layers on a surface of a substrate or on oneof the functional layers applied to the substrate.

The present invention likewise relates to a process for the productionof an electronic device in which at least one layer of the electronicdevice is prepared in that a formulation according to the invention isapplied on a surface and subsequently dried.

The formulations for the preparation of the functional layers can beapplied, for example, by slot-die coating, curtain coating, floodcoating, dip coating, spray coating, spin coating, screen printing,relief printing, gravure printing, rotary printing, roller coating,inkjet printing, flexographic printing, offset printing or nozzleprinting on a surface of a substrate or on one of the functional layersapplied to the substrate.

After the application of a formulation according to the invention to asurface of a substrate or to a functional layer already applied, adrying step can be carried out in order to remove the solvent from thecontinuous phase described above. The drying can preferably be carriedout at relatively low temperature such as room temperature and over arelatively long period in order to avoid bubble formation and to obtaina uniform coating. Preferably, the drying is carried out at a pressurein the range from 10⁻⁶ mbar to 1 bar, particularly preferably in therange from 10⁻⁶ mbar to 100 mbar and especially preferably in the rangefrom 10⁻⁶ mbar to 10 mbar. The duration of the drying depends on thedegree of drying to be achieved, where small amounts of residualsolvents and or other volatile components like e.g. water can optionallybe removed at relatively high temperature and in combination withsintering, which is preferably to be carried out.

The drying step is followed by an annealing step which preferably iscarried out at an elevated temperature in the range from 80 to 300° C.,particularly preferably from 150 to 250° C. and especially preferablyfrom 160 to 220° C. The drying and the annealing step can be combinedand performed as a single step.

It may furthermore be provided that the process is repeated a number oftimes, with formation of different or identical functional layers.Crosslinking of the functional layer formed can take place here in orderto prevent dis-solution thereof, as is disclosed, for example, in EP 0637 899 A1.

The present invention also relates to an electronic device obtainable bya process for the production of an electronic device as described above.

The present invention furthermore relates to an electronic device havingat least one functional layer comprising at least one organic functionalmaterial which is obtainable by the above-mentioned process for theproduction of an electronic device.

An electronic device is taken to mean a device comprising two electrodesand at least one functional layer in between, where this functionallayer comprises at least one organic or organometallic compound.

The organic electronic device is preferably an organicelectroluminescent device (OLED), a polymeric electroluminescent device(PLED), an organic integrated circuit (O-IC), an organic field-effecttransistor (O-FET), an organic thin-film transistor (O-TFT), an organic,light-emitting transistor (O-LET), an organic solar cell (O-SC), anorganic, optical detector, an organic photoreceptor, an organicfield-quench device (O-FQD), an organic electrical sensor, alight-emitting electrochemical cell (LEC) or an organic laser diode(O-laser).

Active components are generally the organic or inorganic materials whichare introduced between the anode and the cathode, where these activecomponents effect, maintain and/or improve the properties of theelectronic device, for example its performance and/or its lifetime, forexample charge-injection, charge-transport or charge-blocking materials,but in particular emission materials and matrix materials. The organicfunctional material which can be employed for the production offunctional layers of electronic devices accordingly preferably comprisesan active component of the electronic device.

Organic electroluminescent devices (OLEDs) are a preferred embodiment ofthe present invention. The OLED comprises a cathode, an anode and atleast one emitting layer.

It is furthermore preferred to employ a mixture of two or more tripletemitters together with a matrix. The triplet emitter having theshorter-wave emission spectrum serves as co-matrix here for the tripletemitter having the longer-wave emission spectrum.

The proportion of the matrix material in the emitting layer in this caseis preferably between 50 and 99.9% by volume, particularly preferablybetween 80 and 99.5% by volume and especially preferably between 92 and99.5% by volume for fluorescent emitting layers and between 70 and 97%by volume for phosphorescent emitting layers.

Correspondingly, the proportion of the dopant is preferably between 0.1and 50% by volume, particularly preferably between 0.5 and 20% by volumeand especially preferably between 0.5 and 8% by volume for fluorescentemitting layers and between 3 and 15% by volume for phosphorescentemitting layers.

An emitting layer of an organic electroluminescent device may alsoencompass systems which comprise a plurality of matrix materials(mixed-matrix systems) and/or a plurality of dopants. In this case too,the dopants are generally the materials whose proportion in the systemis the smaller and the matrix materials are the materials whoseproportion in the system is the greater. In individual cases, however,the proportion of an individual matrix material in the system may besmaller than the proportion of an individual dopant.

The mixed-matrix systems preferably comprise two or three differentmatrix materials, particularly preferably two different matrixmaterials. One of the two materials here is preferably a material havinghole-transporting properties or a wide-band-gap material and the othermaterial is a material having electron-transporting properties. However,the desired electron-transporting and hole-transporting properties ofthe mixed-matrix components may also be combined principally orcompletely in a single mixed-matrix component, where the furthermixed-matrix component(s) fulfil(s) other functions. The two differentmatrix materials may be present here in a ratio of 1:50 to 1:1,preferably 1:20 to 1:1, particularly preferably 1:10 to 1:1 andespecially preferably 1:4 to 1:1. Mixed-matrix systems are preferablyemployed in phosphorescent organic electroluminescent devices. Furtherdetails on mixed-matrix systems can be found, for example, in WO2010/108579.

Apart from these layers, an organic electroluminescent device may alsocomprise further layers, for example in each case one or morehole-injection layers, hole-transport layers, hole-blocking layers,electron-transport layers, electron-injection layers, exciton-blockinglayers, electron-blocking layers, charge-generation layers (IDMC 2003,Taiwan; Session 21 OLED (5), T. Matsumoto, T. Nakada, J. Endo, K. Mori,N. Kawamura, A. Yokoi, J. Kido, Multiphoton Organic EL Device HavingCharge Generation Layer) and/or organic or inorganic p/n junctions. Itis possible here for one or more hole-transport layers to be p-doped,for example with metal oxides, such as MoO₃ or WO₃, or with(per)fluorinated electron-deficient aromatic compounds, and/or for oneor more electron-transport layers to be n-doped. It is likewise possiblefor interlayers, which have, for example, an exciton-blocking functionand/or control the charge balance in the electroluminescent device, tobe introduced between two emitting layers. However, it should be pointedout that each of these layers does not necessarily have to be present.

The thickness of the layers, for example the hole-transport and/orhole-injection layer, can preferably be in the range from 1 to 500 nm,particularly preferably in the range from 2 to 200 nm.

In a further embodiment of the present invention, the device comprises aplurality of layers. The formulation according to the invention canpreferably be employed here for the production of a hole-transport,hole-injection, electron-transport, electron-injection and/or emissionlayer.

The present invention accordingly also relates to an electronic devicewhich comprises at least three layers, but in a preferred embodiment allsaid layers, from hole-injection, hole-transport, emission,electron-transport, electron-injection, charge-blocking and/orcharge-generation layer and in which at least one layer has beenobtained by means of a formulation to be employed in accordance with theinvention.

The device may furthermore comprise layers built up from furtherlow-molecular-weight compounds or polymers which have not been appliedby the use of formulations according to the invention. These can also beproduced by evaporation of low-molecular-weight compounds in a highvacuum.

It may additionally be preferred to use the compounds to be employed notas the pure substance, but instead as a mixture (blend) together withfurther polymeric, oligomeric, dendritic or low-molecular-weightsubstances of any desired type. These may, for example, improve theelectronic or emission properties of the layer.

In a preferred embodiment of the present invention, the organicelectroluminescent device here may comprise one or more emitting layers.If a plurality of emission layers are present, these preferably have aplurality of emission maxima between 380 nm and 750 nm, resultingoverall in white emission, i.e. various emitting compounds which areable to fluoresce or phosphoresce are used in the emitting layers. Veryparticular preference is given to three-layer systems, where the threelayers exhibit blue, green and orange or red emission (for the basicstructure see, for example, WO 2005/011013). White-emitting devices aresuitable, for example, as backlighting of LCD displays or for generallighting applications.

It is also possible for a plurality of OLEDs to be arranged one abovethe other, enabling a further increase in efficiency with respect to thelight yield to be achieved.

In order to improve the out-coupling of light, the final organic layeron the light-exit side in OLEDs can, for example, also be in the form ofa nano-foam, resulting in a reduction in the proportion of totalreflection.

Preference is furthermore given to an OLED in which one or more layersare applied by means of a sublimation process, in which the materialsare applied by vapour deposition in vacuum sublimation units at apressure below 10⁻⁵ mbar, preferably below 10⁻⁶ mbar, particularlypreferably below 10⁻⁷ mbar.

It may furthermore be provided that one or more layers of an electronicdevice according to the invention are applied by means of the OVPD(organic vapour phase deposition) process or with the aid of carrier-gassublimation, in which the materials are applied at a pressure between10⁻⁵ mbar and 1 bar.

It may furthermore be provided that one or more layers of an electronicdevice according to the invention are produced from solution, such as,for example, by spin coating, or by means of any desired printingprocess, such as, for example, screen printing, flexographic printing oroffset printing, but particularly preferably LITI (light induced thermalimaging, thermal transfer printing) or inkjet printing.

These layers may also be applied by a process in which no compound ofthe formula (I) or (II) is employed. An orthogonal solvent canpreferably be used here, which, although dissolving the functionalmaterial of a layer to be applied, does not dissolve the layer to whichthe functional material is applied.

The device usually comprises a cathode and an anode (electrodes). Theelectrodes (cathode, anode) are selected for the purposes of the presentinvention in such a way that their band energies correspond as closelyas possible to those of the adjacent, organic layers in order to ensurehighly efficient electron- or hole-injection.

The cathode preferably comprises metal complexes, metals having a lowwork function, metal alloys or multilayered structures comprisingvarious metals, such as, for example, alkaline-earth metals, alkalimetals, main-group metals or lanthanoids (for example Ca, Ba, Mg, Al,In, Mg, Yb, Sm, etc.). In the case of multilayered structures, furthermetals which have a relatively high work function, such as, for example,Ag, can also be used in addition to the said metals, in which casecombinations of the metals, such as, for example, Ca/Ag or Ba/Ag, aregenerally used. It may also be preferred to introduce a thin interlayerof a material having a high dielectric constant between a metalliccathode and the organic semiconductor. Suitable for this purpose are,for example, alkali-metal or alkaline-earth metal fluorides, but alsothe corresponding oxides (for example LiF, Li₂O, BaF₂, MgO, NaF, etc.).The layer thickness of this layer is preferably between 0.1 and 10 nm,particularly preferably between 0.2 and 8 nm, especially preferablybetween 0.5 and 5 nm.

The anode preferably comprises materials having a high work function.The anode preferably has a potential greater than 4.5 eV vs. vacuum.Suitable for this purpose are on the one hand metals having a high redoxpotential, such as, for example, Ag, Pt or Au. On the other hand,metal/metal oxide electrodes (for example Al/Ni/NiO_(x), Al/PtO_(x)) mayalso be preferred. For some applications, at least one of the electrodesmust be transparent in order to facilitate either irradiation of theorganic material (O-SCs) or the coupling-out of light (OLEDs/PLEDs,O-lasers). A preferred structure uses a transparent anode. Preferredanode materials here are conductive, mixed metal oxides. Particularpreference is given to indium tin oxide (ITO) or indium zinc oxide(IZO). Preference is furthermore given to conductive, doped organicmaterials, in particular conductive, doped polymers, such as, forexample, poly(ethylenedioxythiophene) (PEDOT) and polyaniline (PANI) orderivatives of these polymers. It is furthermore preferred for a p-dopedhole-transport material to be applied as hole-injection layer to theanode, where suitable p-dopants are metal oxides, for example MoO₃ orWO₃, or (per)fluorinated electron-deficient aromatic compounds. Furthersuitable p-dopants are HAT-CN (hexacyanohexaazatriphenylene) or thecompound NPD9 from Novaled. A layer of this type simplifieshole-injection in materials having a low HOMO energy, i.e. an HOMOenergy with a large negative value.

In general, all materials which are used for the layers in accordancewith the prior art can be used in the further layers of the electronicdevice.

The electronic device is correspondingly structured in a manner knownper se, depending on the application, provided with contacts and finallyhermetically sealed, since the lifetime of such devices is drasticallyshortened in the presence of water and/or air.

The formulations according to the invention and the electronic devices,in particular organic electroluminescent devices, obtainable therefromare distinguished over the prior art by one or more of the followingsurprising advantages:

-   1. The electronic devices obtainable using the formulations    according to the invention exhibit very high stability and a very    long lifetime com-pared with electronic devices obtained using    conventional methods.-   2. The formulations according to the invention can be processed    using conventional methods, so that cost advantages can also be    achieved thereby.-   3. The organic functional materials employed in the formulations    according to the invention are not subject to any particular    restrictions, enabling the process of the present invention to be    employed comprehensively.-   4. The layers obtainable using the formulations of the present    invention exhibit excellent quality, in particular with respect to    the uniformity of the layer.

These above-mentioned advantages are not accompanied by an impairment ofthe other electronic properties.

It should be pointed out that variations of the embodiments described inthe present invention fall within the scope of this invention. Eachfeature disclosed in the present invention can, unless this isexplicitly excluded, be replaced by alternative features which serve thesame, an equivalent or a similar purpose. Thus, each feature disclosedin the present invention is, unless stated otherwise, to be regarded asan example of a generic series or as an equivalent or similar feature.

All features of the present invention can be combined with one anotherin any way, unless certain features and/or steps are mutually exclusive.This applies, in particular, to preferred features of the presentinvention. Equally, features of non-essential combinations can be usedseparately (and not in combination).

It should furthermore be pointed out that many of the features, and inparticular those of the preferred embodiments of the present invention,are themselves inventive and are not to be regarded merely as part ofthe embodiments of the present invention. For these features,independent protection can be sought in addition or as an alternative toeach invention presently claimed.

The teaching on technical action disclosed in the present invention canbe abstracted and combined with other examples.

The invention is explained in greater detail below with reference toworking examples, but without being restricted thereby.

The person skilled in the art will be able to use the descriptions toproduce further formulations and electronic devices according to theinvention without the need to employ inventive skill and thus can carryout the invention throughout the claimed range.

WORKING EXAMPLES

All working examples presented below were made using the devicestructure as shown in FIG. 1. The hole-injection layer (HIL) and holetransport layer (HTL) of all examples were prepared by an inkjetprinting process to achieve the desired thickness. For the emissivelayer, the individual solvents used in the Reference and Examples 1 to10 are listed in Table 2 below which shows the boiling point, viscosityand surface tension of the solvents used in the working examples:

TABLE 2 Solvents used in the reference and working examples. Boilingpoint (° C.) Viscosity Surface Working @ 760 mm (mPa · s) tensionExample Solvent(s) used Hg @23° C. (mN/m) Reference 3-Phenoxytoluene 2724.4 37.8 CAS: 3586-14-9 Example Isobutyric acid phenyl 224 2.4 32.0 1ester CAS: 20279-29-2 Example Isobutyric acid p-tolyl 237 2.9 31.2 2ester CAS: 103-93-5 Example Phenyl methacrylate 254 2.9 35.4 3 CAS:2177-70-0 Example Phenyl propionate 215 2.2 31.0 4 CAS: 637-27-4 ExamplePhenyl propionate/ — 2.3 34.0 5 Butylbenzoate (80:20) Example Phenylpropionate/ — 2.7 34.0 6 Butylbenzoate (50:50) Example Benzylisovalerate 250 2.6 33.2 7 CAS: 103-38-8 Example Phenethyl hexanoate 2634.1 33.5 8 CAS: 6290-37-5 Example Ethyl cinnamate 271 6.3 35.9 9 CAS:103-36-6 Example Ethyl 2- 220 6.0 38.5 10 methoxybenzoate CAS: 7335-26-4

The viscosity of the formulations and solvents of the Reference andExamples 1 to 10 was measured using a 1° cone-plate rotational rheometer(type: Haake MARS III Rheometer from Thermo Scientific), where thetemperature and sheer rate are exactly controlled. The viscosities givenin Table 2 are the viscosities of each formulation measured at atemperature of 23.4° C. (+/−0.2° C.) and a sheer rate of 500s⁻¹. Themeasurements were carried out with the following setup: Haake MARS IIIRheometer with bottom plate TMP60 and cone C60/1° Ti L.; N₂ supply witha back-pressure of ˜ 1.8 bar; sample volume of 1.3 mL. Each formulationis measured three times. The stated viscosity value is averaged oversaid measurements. The data processing is performed with the software“Haake RheoWin Job Manager” in accordance with DIN 1342-2. The equipment(Haake MARS III from Thermo Scientific) is regularly calibrated andreceived a certified standard factory calibration before its first use.

The surface tension measurements of the Reference and Examples 1 to 10were performed using the high precision drop shape analysis tool DSA100from Krüss GmbH. The surface tension is determined by the software“DSA4” in accordance with DIN 55660-1. All measurements were performedat room temperature being in the range between 22° C. and 24° C. Thestandard operating procedure includes the determination of the surfacetension of each formulation (sample volume of 0.3 mL) using a freshdisposable drop dispensing system (syringe and needle). Each drop ismeasured over the duration of one minute with sixty measurements whichare later on averaged. For each formulation three drops are measured.The final value is averaged over said measurements. The tool isregularly cross-checked against various liquids having known surfacetension.

The solvent(s) which are used for the green emitting layer (G-EML) inthe Reference and Examples 1 to 10 and the respective concentration,viscosity and surface tension of the prepared inks are shown in Table 3below.

TABLE 3 Concentration, viscosity and surface tension of the inksprepared in the reference and working examples (assuming ideal mixturesfor solvent mixtures in example 5 and 6). Working ConcentrationViscosity Surface Example Layer (weight-%) (mPa · s) Tension (mN/m)Reference G-EML 1.332 4.65 37.8 Example 1 G-EML 1.386 2.4 32.0 Example 2G-EML 1.410 2.9 31.2 Example 3 G-EML 1.328 2.9 35.4 Example 4 G-EML1.333 2.6 31.0 Example 5 G-EML 1.344 2.3 34.1 Example 6 G-EML 1.359 2.734.0 Example 7 G-EML 1.417 2.6 33.2 Example 8 G-EML 1.442 4.1 33.5Example 9 G-EML 1.335 6.3 35.9 Example 10 G-EML 1.259 6.0 38.5

Description of the Fabrication Process

Glass substrates covered with pre-structured ITO and bank material werecleaned using ultrasonication in isopropanol followed by de-ionizedwater, then dried using an air-gun and a subsequent annealing on ahot-plate at 230° C. for 2 hours.

A hole-injection layer (HIL) using PEDOT-PSS (Clevios A14083, Heraeus)was inkjet-printed onto the substrate and dried in vacuum. The HIL wasthen annealed at 185° C. for 30 minutes in air.

On top of the HIL, a hole-transport layer (HTL) was inkjet-printed,dried in vacuum and annealed at 210° C. for 30 minutes in nitrogenatmosphere. As material for the hole-transport layer polymer HTM-1 wasused. The structure of the polymer HTM-1 is the following:

The green emissive layer (G-EML) was also inkjet-printed, vacuum driedand annealed at 160° C. for 10 minutes in nitrogen atmosphere. The inkfor the green emissive layer contained in all working examples two hostmaterials (i.e. HM-1 and HM-2) as well as one triplett emitter (EM-1).The materials were used in the following ratio: HM-1:HM-2:EM-1=40:40:20.Only the solvent(s) differ from example to example, as can be seen fromTable 2 above. The structures of the materials are the following:

All the inkjet printing processes were performed under yellow light andunder ambient conditions.

The devices were then transferred into the vacuum deposition chamberwhere the deposition of a common hole blocking layer (HBL), anelectron-transport layer (ETL), and a cathode (AI) was done usingthermal evaporation (see FIG. 1). The devices were then characterized inthe glovebox.

In the hole blocking layer (HBL) ETM-1 was used as a hole-blockingmaterial. The material has the following structure:

In the electron transport layer (ETL) a 50:50 mixture of ETM-1 and LiQwas used. LiQ is lithium 8-hydroxyquinolinate.

Finally, the Al electrode is vapor-deposited. The devices were thenencapsulated in a glove box and physical characterization was performedin ambient air.

Measurement methods for the Reference and Examples 1 to 6 and 10 Thedevices are driven with constant voltage provided by a Keithley 230voltage source. The voltage over the device as well as the currentthrough the device are measured with two Keithley 199 DMM multimeters.The brightness of the device is detected with a SPL-025Y brightnesssensor, a combination of a photodiode with a photonic filter. The photocurrent is measured with a Keithley 617 electrometer. For the spectra,the brightness sensor is replaced by a glass fiber which is connected tothe spectrometer input. The device lifetime is measured under a givencurrent with an initial luminance. The luminance is then measured overtime by a calibrated photodiode.

Measurement methods for Examples 7 to 9 To measure the OLED performancein current density-luminance-voltage performance, the device is drivenby sweeping voltage from −5V to +25 V provided by a Keithley 2400 sourcemeasure unit. The voltage over the OLED device as well as the currentthrough the OLED devices are recorded by the Keithley 2400 SMU. Thebrightness of the device is detected with a calibrated photodiode. Thephoto current is measured with a Keithley 6485/E picoammeter. For thespectra, the brightness sensor is replaced by a glass fiber which isconnected to an Ocean Optics USB2000+ spectrometer.

Results and Discussion Reference and Examples 1 to 6

Inkjet printed OLED devices were prepared with the printed layer usingthe respective solvent(s) as shown in Table 2 above for the greenemissive layer (G-EML). FIG. 1 shows the device structure. Theefficiencies of Examples 1 to 6 show comparable or slightly highervalues than the Reference. This indicates that the solvents in Examples1 to 6 show better film formation during drying. Table 4 belowsummarizes the device efficiencies of the Reference and Examples 1 to 6.

TABLE 4 Luminance efficiency and external quantum efficiency (EQE) ofReference and Examples 1 to 6. External quantum Luminance efficiencyefficiency (EQE) [%] Working Example [cd/A] at 1000 cd/m² at 1000 cd/m²Reference 51.69 14.38 Example 1 53.95 14.73 Example 2 59.34 16.53Example 3 50.30 14.05 Example 4 54.23 14.90 Example 5 54.90 15.01Example 6 54.32 14.80

Example 7

An inkjet printed OLED device was prepared with the printed layer usingbenzyl isovalerate as solvent for the green emissive layer (G-EML). Thebank was pre-fabricated on the substrate to form the pixelated device.In this case, the green emissive materials were dissolved in benzylisovalerate at a concentration of 1.417 weight-%. The luminanceefficiency at 1000 cd/m² is 53.46 cd/A. The efficiency of the OLEDdevice is very good and the voltage at 1000 cd/m² is 7.13 V.

Example 8

An inkjet printed OLED device was prepared with the printed layer usingphenethyl hexanoate as solvent for the green emissive layer (G-EML). Thebank was pre-fabricated on the substrate to form the pixelated device.In this case, the green emissive materials dissolved in phenethylhexanoate at a concentration of 1.442 weight-%. The luminance efficiencyat 1000 cd/m² is 48.89 cd/A. The efficiency of the OLED device is verygood and the voltage at 1000 cd/m² is 5.92 V.

Example 9

An inkjet printed OLED device was prepared with the printed layer usingethyl cinnamate as solvent for the green emissive layer (G-EML). Thebank was pre-fabricated on the substrate to form the pixelated device.In this case, the green emissive materials dissolved in ethyl cinnamateat a concentration of 1.335 weight-%. The luminance efficiency at 1000cd/m² is 57.54 cd/A. The efficiency of the OLED device is very good andthe voltage at 1000 cd/m² is 7.11 V.

Example 10

Inkjet printed OLED devices were prepared with the printed layer usingthe respective solvent(s) as shown in Table 6 above for the greenemissive layer (G-EML). FIG. 1 shows the device structure. Theefficiencies of Examples 10 show comparable values as the Reference. Theluminance efficiency at 1000 cd/m² is 50.23 cd/A and the externalquantum efficiency is 13.94% The efficiency of the OLED device is verygood and the voltage at 1000 cd/m² is 7.11 V.

The solvent system of the present invention provides a wider processwindow and an improved device performance and helps to meet thedifferent criteria of various inkjet printing machines having differentprint heads and physical requirements.

1.-41. (canceled)
 42. A formulation comprising (A) at least one estersolvent according to General Formula (II):

wherein R¹ is H or R³; R² is H or R³; and R³ may be the same ordifferent from each other and is on each occasion selected independentlyfrom the group consisting of hydrogen, straight-chain alkyl groupshaving from 1 to 12 carbon atoms, straight-chain alkenyl or alkynylgroups having from 2 to 12 carbon atoms, branched-chain alkyl or alkenylgroups having from 3 to 12 carbon atoms and branched-chain alkynylgroups having from 4 to 12 carbon atoms, wherein one or morenon-adjacent CH₂ groups may be optionally replaced by —O—, —S—, or—Si(R⁵)₂—; or R¹ and R² taken together represent ═CH₂; and R³ isselected from the group consisting of hydrogen, straight-chain alkylgroups having from 1 to 12 carbon atoms, straight-chain alkenyl oralkynyl groups having from 2 to 12 carbon atoms, branched-chain alkyl oralkenyl groups having from 3 to 12 carbon atoms and branched-chainalkynyl groups having from 4 to 12 carbon atoms, wherein one or morenon-adjacent CH₂ groups may be optionally replaced by —O—, —S—, or—Si(R⁵)₂—; and wherein X on each occasion is selected independently fromN or CR⁴ with the provision that no more than three X are selected as N;R⁴ on each occasion is selected independently from the group consistingof hydrogen, straight-chain alkyl or alkoxy groups having from 1 to 12carbon atoms, straight-chain alkenyl or alkynyl groups having from 2 to12 carbon atoms, branched-chain alkyl, alkoxy or alkenyl groups havingfrom 3 to 12 carbon atoms, branched-chain alkynyl groups having from 4to 12 carbon atoms and SiR⁵ ₃; R⁵ on each occasion is selectedindependently from the group consisting of hydrogen, straight-chainalkyl or alkoxy groups having from 1 to 12 carbon atoms andbranched-chain alkyl or alkoxy groups having from 3 to 12 carbon atoms;Q² is absent or an alkylene group having from 1 to 10 carbon atoms whichmay optionally contain one or more double bonds and which may optionallybe substituted with one or more alkyl groups having from 1 to 4 carbonatoms, wherein two alkyl groups may be bonded together to form amonocyclic ring system together with the carbon atoms of said alkylenegroup; and with the proviso that if Q² is absent, X on each occasion isCR⁴, wherein at least one R⁴ is a straight-chain alkoxy group havingfrom 1 to 12 carbon atoms or a branched-chain alkoxy group having from 3to 12 carbon atoms; and (B) at least one organic functional materialselected from the group consisting of organic conductors, organicsemiconductors, organic fluorescent compounds, organic phosphorescentcompounds, organic light-absorbent compounds, organic light-sensitivecompounds, organic photosensitisation agents and other organicphotoactive compounds, selected from organometallic complexes oftransition metals, rare earth metals, lanthanides and actinides.
 43. Theformulation according to claim 42, wherein the ester solvent accordingto General Formula (II) is selected from the group consisting of GeneralFormulae (II-a) to (II-i):

wherein Q² is an alkylene group having from 1 to 6 carbon atoms whichmay optionally contain one or more double bonds and which may optionallybe substituted with one or more alkyl groups having from 1 to 4 carbonatoms, wherein two alkyl groups may be bonded together to form amonocyclic ring system together with the carbon atoms of said alkylenegroup.
 44. The formulation according to claim 42, wherein R⁴ on eachoccasion is selected independently from the group consisting ofhydrogen, straight-chain alkyl or alkoxy groups having from 1 to 6carbon atoms, straight-chain alkenyl or alkynyl groups having from 2 to6 carbon atoms, branched-chain alkyl, alkoxy or alkenyl groups havingfrom 3 to 6 carbon atoms, branched-chain alkynyl groups having from 4 to6 carbon atoms and SiR⁵ ₃, wherein R⁵ on each occasion is selectedindependently from the group consisting of hydrogen, straight-chainalkyl or alkoxy groups having from 1 to 6 carbon atoms andbranched-chain alkyl or alkoxy groups having from 3 to 6 carbon atoms.45. The formulation according to claim 42, wherein the ester solventaccording to General Formula (II) is selected from the group consistingof General Formulae (II-a1), (II-a2), (II-a3), (II-c1) and (II-d1):


46. The formulation according to claim 42, wherein R¹ is H or R³; R² isH or R³; and R³ on each occasion is selected independently from thegroup consisting of hydrogen, methyl, ethyl, propyl, butyl, pentyl,hexyl, heptyl, octyl, nonyl and decyl and their isomers; or wherein R¹and R² taken together represent ═CH₂; and R³ is selected from the groupconsisting of hydrogen, methyl, ethyl, propyl, butyl, pentyl, hexyl,heptyl, octyl, nonyl and decyl and their isomers.
 47. The formulationaccording to claim 46, wherein R¹ is H or R³; R² is H or R³; and R³ oneach occasion is selected independently from the group consisting ofhydrogen, methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl,sec-butyl, t-butyl, n-pentyl, 2-pentyl, 3-pentyl, 2-methylbutyl,3-methylbutyl, 3-methylbut-2-yl, 2-methylbut-2-yl, 2,2-dimethylpropyl,n-hexyl, 2-hexyl, 3-hexyl, 2-methylpentyl, 3-methylpentyl,4-methylpentyl, 2-methylpent-2-yl, 3-methylpent-2-yl, 2-methylpent-3-yl,3-methylpent-3-yl, 2-ethylbutyl, 3-ethylbutyl, 2,3-dimethylbutyl,2,3-dimethylbut-2-yl, 2,2-dimethylbutyl, n-heptyl, n-octyl, n-nonyl andn-decyl; or wherein R¹ and R² taken together represent ═CH₂; and R³ isselected from the group consisting of hydrogen, methyl, ethyl, n-propyl,iso-propyl, n-butyl, iso-butyl, sec-butyl, t-butyl, n-pentyl, 2-pentyl,3-pentyl, 2-methylbutyl, 3-methylbutyl, 3-methylbut-2-yl,2-methylbut-2-yl, 2,2-dimethylpropyl, n-hexyl, 2-hexyl, 3-hexyl,2-methylpentyl, 3-methylpentyl, 4-methylpentyl, 2-methylpent-2-yl,3-methylpent-2-yl, 2-methylpent-3-yl, 3-methylpent-3-yl, 2-ethylbutyl,3-ethylbutyl, 2,3-dimethylbutyl, 2,3-dimethylbut-2-yl,2,2-dimethylbutyl, n-heptyl, n-octyl, n-nonyl and n-decyl.
 48. Theformulation according to claim 42, wherein the ester solvent is liquidat room temperature.
 49. The formulation according to claim 42, whereinthe ester solvent has a boiling point of 400° C. or below, wherein theboiling point is measured at a pressure of 760 mm Hg.
 50. Theformulation according to claim 42, wherein the formulation has aviscosity in the range from 0.8 to 50 mPa·s.
 51. The formulationaccording to claim 42, wherein the formulation has a surface tension inthe range from 15 to 80 mN/m.
 52. The formulation according to claim 42,wherein the ester solvent has a boiling point in the range from 200° C.to 290° C., wherein the boiling point is measured at a pressure of 760mm Hg, a viscosity in the range from 2 to 10 mPa·s. and a surfacetension in the range from 28 to 35 mN/m.
 53. The formulation accordingto claim 42, wherein the content of the ester solvent is in the rangefrom 0.5 to 100 Vol.-%, based on the total amount of solvents in theformulation.
 54. The formulation according to claim 42, wherein theformulation contains at least one additional solvent which is asubstituted and non-substituted aromatic or linear esters, substitutedor non-substituted arene derivatives, indane derivatives, substitutedand non-substituted heterocycles, fluorinated or chlorinatedhydrocarbons; or linear or cyclic siloxanes
 55. The formulationaccording to claim 42, wherein the formulation contains at least oneadditional solvent selected from the group consisting of ethyl benzoate,butyl benzoate, 3-phenoxytoluene, anisole derivatives, xylene,hexamethylindane, substituted and non-substituted aromatic or linearketones, pyrrolidinones, pyridines; fluorinated or chlorinatedhydrocarbons, and linear or cyclic siloxanes.
 56. The formulationaccording to claim 42, wherein the organic functional material has asolubility in the range from 1 to 250 g/l.
 57. The formulation accordingto claim 42, wherein the content of the organic functional material inthe formulation is in the range from 0.001 to 20 weight-%, based on thetotal weight of the formulation.
 58. The formulation according to claim42, wherein the at least one organic functional material is selectedfrom the group consisting of fluorescent emitters, phosphorescentemitters, host materials, matrix materials, exciton-blocking materials,electron-transport materials, electron-injection materials,hole-transport materials, hole-injection materials, n-dopants,p-dopants, wide-band-gap materials, electron-blocking materials andhole-blocking materials.
 59. The formulation according to claim 42,wherein the organic semiconductor is a polymeric compound, anon-polymeric compound or a blend of a polymeric compound and anon-polymeric compound.
 60. A process for the preparation of theformulation according to claim 42, which comprises mixing the estersolvent, the optional further solvent and the at least one organicfunctional material.
 61. A process for the production of an electronicdevice, which comprises applying at least one formulation according toclaim 42 on a surface of a layer of the electronic device andsubsequently dried.
 62. An electronic device which is obtainable by theprocess according to claim 61.